2 of 454

The p-block Elements

Noble gases or Inert gases

Halogens

Non metals

Metalloids

Metals

Electronic configuration = ns² np^1-6

EXCEPT, He with 1s²

Groups

3 of 454

The p-block Elements

Boron also found in cell wall

Silicon used in computer chips

Borax used in optical glasses

C found as graphite in pencils

C as diamond

4 of 454

12C07.1��General Concepts about group 15 elements��

5 of 454

��12C07.1 General Concepts about group 15 elements��

Learning Objectives

Basic Concepts of group 15 elements

Physical properties of group 15 elements

Chemical properties of group 15 elements

Anomalous behavior of nitrogen

6 of 454

12C07.1

CV 1

Basic Concepts of group 15 elements

7 of 454

��Basic Concepts about group 15 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Nitrogen	N	7	14.01	Non metal
Phosphorus	P	15	30.97	Non metal
Arsenic	As	33	74.92	Metalloid
Antimony	Sb	51	121.75	Metalloid
Bismuth	Bi	83	208.98	Metal
Moscovium	Mc	115	289	Metal

8 of 454

��Basic Concepts about group 15 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Nitrogen	N	7	14.01	Non metal
Phosphorus	P	15	30.97	Non metal
Arsenic	As	33	74.92	Metalloid
Antimony	Sb	51	121.75	Metalloid
Bismuth	Bi	83	208.98	Metal
Moscovium	Mc	115	289	Metal

9 of 454

��Basic Concepts about group 15 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Nitrogen	N	7	14.01	Non metal
Phosphorus	P	15	30.97	Non metal
Arsenic	As	33	74.92	Metalloid
Antimony	Sb	51	121.75	Metalloid
Bismuth	Bi	83	208.98	Metal
Moscovium	Mc	115	289	Metal

10 of 454

��Basic Concepts about group 15 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Nitrogen	N	7	14.01	Non metal
Phosphorus	P	15	30.97	Non metal
Arsenic	As	33	74.92	Metalloid
Antimony	Sb	51	121.75	Metalloid
Bismuth	Bi	83	208.98	Metal
Moscovium	Mc	115	289	Metal

11 of 454

��Basic Concepts about group 15 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Nitrogen	N	7	14.01	Non metal
Phosphorus	P	15	30.97	Non metal
Arsenic	As	33	74.92	Metalloid
Antimony	Sb	51	121.75	Metalloid
Bismuth	Bi	83	208.98	Metal
Moscovium	Mc	115	289	Metal

12 of 454

��Basic Concepts about group 15 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Nitrogen	N	7	14.01	Non metal
Phosphorus	P	15	30.97	Non metal
Arsenic	As	33	74.92	Metalloid
Antimony	Sb	51	121.75	Metalloid
Bismuth	Bi	83	208.98	Metal
Moscovium	Mc	115	289	Metal

General Electronic Configuration – ns²np³

EXTRA STABLE

13 of 454

Occurrence of group 15 elements

Nitrogen

N₂ - 78% by volume

Chile saltpeter NaNO₃

Indian saltpeter KNO₃

Constituent in plants & animals

Amino acids in proteins

NH₂

CH₃

COOH

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Occurrence of group 15 elements

Nitrogen

N₂ - 78% by volume

Chile saltpeter NaNO₃

Indian saltpeter KNO₃

Constituent in plants & animals

DNA

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Occurrence of group 15 elements

Phosphorus

Apatite

Ca₉(PO₄)₆ .CaX₂

ATP

ADP

Bones

Egg yolk

16 of 454

Occurrence of group 15 elements

As, Sb, Bi

Present in sulphide minerals

As₂S₃ and Sb₂S₃ sulphide ore

Bi sulphide ore (Bi₂S₃)

Moscovium

Synthetic Radioactive element

Short Half life

Little amount

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12C07.1

CV 2

Physical Properties of group 15 elements

18 of 454

Electronic configuration

Name of element	Symbol of element	Electronic configuration
Nitrogen	N	[He]2s²2p³
Phosphorus	P	[Ne]3s²3p³
Arsenic	As	[Ar]3d¹⁰4s²4p³
Antimony	Sb	[Kr]4d¹⁰5s²5p³
Bismuth	Bi	[Xe]5d¹⁰6s²6p³

Filled inner d orbitals

d-orbitals not present

19 of 454

Trends in physical properties of group 15 elements

Atomic and ionic radii

Symbol of element	Atomic radii/pm
N	70
P	110
As	121
Sb	141
Bi	148

Number

of shells

increase

Atomic size

increase

Considerable increase in atomic radii due to effective shielding of s and p electrons

Small increase due to ineffective shielding of d and f electrons

Electronic configuration
[He]2s²2p³
[Ne]3s²3p³
[Ar]3d¹⁰4s²4p³
[Kr]4d¹⁰5s²5p³
[Xe]5d¹⁰6s²6p³

20 of 454

Symbol of element	Ionization energy (kJ/mol)
N	1402
P	1012
As	947
Sb	834
Bi	703

Ionization Enthalpy

Ionization

Enthalpy

Decrease

Atomic radii increase

Nucleus attraction

towards valence e^– decrease

NOTE – ΔH₁<ΔH₂<ΔH₃

Ionization enthalpy greater than group 14 and group 16 element due to extra stable half filled electronic configuration

Energy absorbed when an electron is removed from the outermost shell of an isolated gaseous atom.

21 of 454

Symbol of element	Electronegativity
N	3.0
P	2.1
As	2.0
Sb	1.9
Bi	1.9

Electronegativity

Atomic radii increase

Electronegativity

decrease

Ability of an atom to attract shared pair of electrons in a bond of molecule

Greater than group 14 elements due to greater effective nuclear charge of group 15 elements

Atom A

Weak Pull

Atom B

Strong pull

Z^*_eff decrease

22 of 454

Symbol of element	M.P/K	B.P/K
N	63*	77.2*
P	317	554
As	1089	888
Sb	904	1860
Bi	544	1837

Atomic

Mass

increase

Boiling point

increase

Increase in M.P due to atomic mass

Decrease in M.P is

due to difference

In packing

Melting point and boiling point

‘ * ‘ shows M.P & B.P is measured for N₂

23 of 454

Name of element	Symbol of element	Characteristic
Nitrogen	N	Non metal
Phosphorus	P	Non metal
Arsenic	As	Metalloid
Antimony	Sb	Metalloid
Bismuth	Bi	Metal
Moscovium	Mc	Metal

Metallic and non-metallic character

Atomic radii

increase

Ionization enthalpy

decrease

Metallic character

increase

24 of 454

Name of element	Symbol of element
Nitrogen	N
Phosphorus	P
Arsenic	As
Antimony	Sb
Bismuth	Bi

Physical State

Gaseous

Solid

Red P

25 of 454

Q. Why ionization energy of group 15 elements is larger than both group 14 and group 16 elements?

Pause the video

Time duration - 2 min

26 of 454

Q. Why ionization energy of group 15 elements is larger than both group 14 and group 16 elements?

Sol. On going from left to right effective nuclear charge increase, thus outer electron is more tightly held and thus

difficult to remove

Z^*_eff [ group 15 ] > Z^*_eff [ group 14 ]

Thus difficulty to remove outer electron – group 15 > group 14

Thus I.E of Group 15 > group 14

Valence shell Electronic configuration –

Group 15 Group 16

Half filled Will become half filled after removing electron

Extra stable Will become extra stable after removing electron

Thus, I.E of Group 15 > I.E of Group 16

Remove 1 electron

27 of 454

12C07.1

CV 3

Chemical Properties of group 15 elements

28 of 454

Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5

Common Oxidation state (O.S) is -3, +3, +5

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Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5
P	+5,+3,-3

Common Oxidation state (O.S) is -3, +3, +5

30 of 454

Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5
P	+5,+3,-3
As	+5,+3

Common Oxidation state (O.S) is -3, +3, +5

31 of 454

Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5
P	+5,+3,-3
As	+5,+3
Sb	+5,+3

Common Oxidation state (O.S) is -3, +3, +5

32 of 454

Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5
P	+5,+3,-3
As	+5,+3
Sb	+5,+3
Bi	+3

Common Oxidation state (O.S) is -3, +3, +5

33 of 454

Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5
P	+5,+3,-3
As	+5,+3
Sb	+5,+3
Bi	+3

+1 to +4 O.S disproportionate

Show +1,+2,+4,+5 O.S with oxygen

Doesn’t show +5 O.S with halogens

Maximum covalency is 4

Common Oxidation state (O.S) is -3, +3, +5

Elements in +5 O.S are oxidising agents

34 of 454

Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5
P	+5,+3,-3
As	+5,+3
Sb	+5,+3
Bi	+3

Form oxoacids in

+1 and +4 O.S

Common Oxidation state (O.S) is -3, +3, +5

Elements in +5 O.S are oxidising agents

35 of 454

Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5
P	+5,+3,-3
As	+5,+3
Sb	+5,+3
Bi	+3

Does not form +5

oxidation state

Common Oxidation state (O.S) is -3, +3, +5

Elements in +5 O.S are oxidising agents

36 of 454

Oxidation state of group 15 elements

Symbol of element	Oxidation state
N	-3 to +5
P	+5,+3,-3
As	+5,+3
Sb	+5,+3
Bi	+3

Inert Pair effect

No. of shells

increase

Addition of d and f electron

increase

Ineffective shielders of valence electron

Nuclear charge towards valence e^–

decrease

Stability

Of +5 O.S

decrease

Inability of s - electrons to participate in bonding due to increased nuclear charge

37 of 454

Reactions of group 15 elements

Reaction with metal

Reaction with hydrogen

Reaction with halogen

Reaction with Oxygen

Group 15 elements show –3 oxidation state and form binary compounds with metals

Example – Ca₃N₂ , Ca₃P₂

Na₃As, Zn₃Sb₂

38 of 454

Reactions of group 15 elements

Reaction with hydrogen

EH₃ type hydrides are formed [ E = 15 group elements]

Order of stability of hydrides

STABILITY ORDER : NH₃ > PH₃> AsH₃> SbH₃> BiH₃

2p – 1s

3p – 1s

4p – 1s

5p – 1s

OVERLAPPING ORDER : 2p – 1s > 3p – 1s > 4p – 1s > 5p – 1s

Basicity of hydrides

NH₃ > PH₃> AsH₃> SbH₃> BiH₃

Due to small size of N, electron density is more and hence stronger Lewis base

39 of 454

Reactions of group 15 elements

Reaction with hydrogen

EH₃ type hydrides are formed [ E = 15 group elements]

Reducing nature of Hydrides

Reducing nature - NH₃< PH₃< AsH₃< SbH₃< BiH₃

BOND LENGTH : NH₃< PH₃< AsH₃< SbH₃< BiH₃

40 of 454

Reactions of group 15 elements

Reaction with hydrogen

EH₃ type hydrides are formed [ E = 15 group elements]

Melting point and boiling point

Solubility in water

NH₃ is most soluble due to hydrogen bonding with water

Due to hydrogen bonding of NH₃ in solid as well as liquid state,

NH₃ has the highest M.P & B.P

Smaller in size and highly electronegative

+δ

�

+δ

�

+δ

�

+δ

�

+δ

�

-δ

�

-δ

�

41 of 454

Reactions of group 15 elements

Reaction with Oxygen

E₂O₅ & E₂O₃ type [E is element]

E₂O₅ more acidic than E₂O₃ as element is in +5 O.S so more electron deficient than +3 O.S thus E₂O₅ act as stronger lewis acid

N₂O₃	P₂O₃	As₂O₃	Sb₂O₃	Bi₂O₃

Acidic character decrease

Purely acidic

Amphoteric

Basic

Symbol of element
N
P
As
Sb
Bi

Metallic Character

increase

Metal forms basic oxides while non metals form acidic oxides and metalloids form amphoteric oxide

42 of 454

Reactions of group 15 elements

Reaction with halogen

EX₅ & EX₃ type [X is halogen]

N does not form NX₅ due to unavailability of d – orbitals

So N cannot expand its octet to show +5 O.S

Pentahalides more covalent than trihalides

Fajan’s Rule

E ⁺³

E ⁺⁵

Less polarizing power

More polarizing power

43 of 454

Fajan’s rule predicting covalent character of halides

NX₃	PX₃	AsX₃	SbX₃	BiX₃

Polarizing power decrease due to increase in atomic size of element

Covalent Character decrease

Halogen (X)
Fluorine
Chlorine
Bromine
Iodine
Astatine

Anionic

Size increase

Covalentcharacter

increase

Ease of polarization

increase

Example - BiF₃ is an ionic compound whereas BiI₃ is covalent compound

Only NF₃ is known to be stable due to small size of N

Covalentcharacter

increase

Covalentcharacter

increase

44 of 454

Q. Why is BiH₃ strongest reducing agent among group 15 hydrides ?

Pause the video

Time duration - 2 min

45 of 454

Q. Why is BiH₃ strongest reducing agent among group 15 hydrides ?

Sol. BiH₃ has longer bond length between the Bi – H as compared to other hydrides

2p – 1s

3p – 1s

4p – 1s

5p – 1s

Weakest overlapping

Extent of Overlapping decrease

Bond length increase

Ease of removal of H increase & thus reducing nature increase

46 of 454

PSV 01

12C07.1

47 of 454

Q. The HNH bond angle value is higher than HPH, HAsH & HSbH angles. Why ?

Pause the video

Time duration - 2 min

NCERT, Exercise Question – 7.9

Page no. – 213

48 of 454

Q. The HNH bond angle value is higher than HPH, HAsH & HSbH angles. Why ?

Sol.

sp³

s character of in a bond ∝ Bond angle

s Character of orbital – sp³ > 3p

Bond angle between bonds – sp³ > 3p

49 of 454

PSV 02

12C07.1

50 of 454

Q. Explain why NH₃ is basic while BiH₃ is only feebly basic ?

Pause the video

Time duration - 2 min

NCERT, Exercise Question – 7.11

Page no. – 213

51 of 454

Q. Explain why NH₃ is basic while BiH₃ is only feebly basic ?

Sol.

Small size

More electron

density

Thus stronger Lewis

base

Large size

Less electron

density

Thus weaker Lewis

base

52 of 454

ConcepTest

Ready for challenge

53 of 454

Q. Bond angle in PH₄⁺ is higher than in PH₃. Why ?

Pause the video

Time duration - 2 min

NCERT, Intext Question – 7.7 (a)

Page no. – 182

54 of 454

Q. Bond angle in PH₄⁺ is higher than in PH₃. Why ?

Sol.

Bond pair – bond pair

repulsion

Lone pair – bond pair

repulsion

Bond pair – bond pair repulsion < Lone pair – bond pair repulsion

Bond angle in PH₃ decrease more than in PH₄⁺

55 of 454

12C07.1

CV 4

Anomalous behavior of Nitrogen

56 of 454

Anomalous behavior of N

Anomalous Behavior of nitrogen

Due to characteristics of N

Small size

Attraction of electrons due

to high electronegativity of N

High ionization energy

No d orbital

57 of 454

Anomalous behavior of N

Anomalous Behavior of nitrogen

Weaker catenation property

Size of atoms is small

Bond Length less

Higher interelectronic repulsion of lone pair of electrons

Single bond will be weak

Weaker catenation Property

Bond Strength

Inability to form dπ – pπ multiple bond

P can form dπ – pπ bond

R₃P=O

R₃P=CH₂

P & As can form dπ – dπ bond

With transition metal acting as ligand such as P(C₂H₅)₃ & As(C₂H₅)₃

58 of 454

Anomalous behavior of N

Anomalous Behavior of nitrogen

Ability to form pπ – pπ multiple bond

As we go down the group size of orbital become more diffused

Strong overlapping

Weak overlapping

59 of 454

PSV 03

12C07.1

60 of 454

Q. Why does R₃P=O exist but R₃N=O does not ? R = alkyl group

Pause the video

Time duration - 2 min

NCERT, Exercise Question – 7.10

Page no. – 213

61 of 454

Q. Why does R₃P=O exist but R₃N=O does not ? R = alkyl group

Sol. For NITROGEN (N)

Normally

Maximum

Maximum N can form 4 bonds but R₃N=O, N is forming 5

Bonds which is not possible

For PHOSPHORUS (P)

P has d orbital to accommodate electrons given by O thus can form more than 4 bonds

62 of 454

Summary

1.) General electronic configuration of group 15 elements is ns²np³

Symbol of element	Atomic radii/pm
N	70
P	110
As	121
Sb	141
Bi	148

Electronic configuration
[He]2s²2p³
[Ne]3s²3p³
[Ar]3d¹⁰4s²4p³
[Kr]4d¹⁰5s²5p³
[Xe]5d¹⁰6s²6p³

I.E

decrease

Electro

negativity

decrease

Metallic

Character inc.

Atomic

radii inc.

B.P

inc.

2.) Common oxidation states are -3, +3, +5

3.) These elements react with hydrogen to form hydrides of EH₃ type.

4.) These elements react with oxygen to form oxides of E₂O₃ & E₂O₅ type.

Stability Of

+5 O.S dec.

5.) These elements react with halogen to form halides of EX₃ & EX₅ type.

63 of 454

Reference Questions

Intext Question, NCERT : 7.1, Page no. – 174

Example Question, NCERT : 7.1, Page no. – 174

7.2, Page no. – 174

7.3, Page no. – 174

Exercise Question, NCERT : 7.1, Page no. – 213

Workbook Questions: 1, 2, 3, 11, 12

64 of 454

12C07.2��Important compounds of group 15 elements��

65 of 454

��12C07.2 Important compounds of group 15 elements��

Learning Objectives

Dinitrogen

Ammonia

Oxides of Nitrogen

Nitric acid

Phosphine

Phosphorus Halides

Oxoacids of Phosphorus

66 of 454

12C07.2

CV1

Dinitrogen

67 of 454

Dinitrogen

Preparation of N₂

Fractional Distillation

Air Intake

Air heats up as it

is compressed

Liquid N₂

Compressed air is

cooled

Compressed air is

Allowed to expand and

Turn into liquid

Liquefied air in at -200^o C

Oxygen

Nitrogen

90 K

77.2 K

Compressor

68 of 454

Dinitrogen

Laboratory preparation

NH₄Cl(aq) + NaNO₂(aq) N₂(g) + 2H₂O(l) + NaCl(aq)

NO & HNO₃ impurities are removed by passing gas through aqueous solution of H₂SO₄ containing K₂Cr₂O₇

Preparation of N₂

69 of 454

Dinitrogen

Dinitrogen (N₂)

Laboratory preparation

(NH₄)₂ Cr₂O₇ N₂ + 4H₂O + Cr₂O₃

Very pure N₂ can be obtained by thermal decomposition of Ba(N₃)₂ or NaN₃

Ba(N₃)₂ Ba + 3N₂

Heat

Preparation of N₂

70 of 454

Dinitrogen

Dinitrogen (N₂)

Properties of N₂

Physical Properties

Colorless, tasteless, odorless, non toxic

Stable Isotopes

Electrons

Neutrons

Protons

Solubility in water

Very less soluble in water due to zero polarity in molecule

Low Freezing point and boiling point

¹⁴N

¹⁵N

71 of 454

Dinitrogen

Dinitrogen (N₂)

Properties of N₂

Chemical Properties

N₂ is very unreactive due to its high bond dissociation enthalpy

As temperature increases reactivity increases

Combination with metals

6Li + N₂ 2Li₃N

3Mg + N₂ Mg₃N₂

Heat

Formation of ammonia

N₂(g) + 3H₂(g) 2NH₃(g)

⇌

Takes place at 773 K

_f H^o = - 46.1 kJ/mol

Reaction with oxygen

N₂ + O₂ 2NO

⇌

Takes place at 2000 K

72 of 454

Dinitrogen

Dinitrogen (N₂)

Uses of N₂

Liquid N₂ as refrigerant

Born haber process

N₂

3H₂

2 NH₃

Creating inert atmosphere in iron and steel industry

Formation of important compounds such as cyanogen

73 of 454

Q. Why N₂ is less reactive at room temperature ?

Pause the video

Time duration - 2 min

NCERT, Intext Question – 7.3

Page no. – 175

74 of 454

Q. Why N₂ is less reactive at room temperature ?

Sol.

Hybridization - sp

1 σ

2 π

Multiple bond means

bond length is extremely small

As there are 2 π overlap

Bond dissociation energy

Reactivity

Bond length = 109.8 pm

Bond dissociation energy = 946 kJ/mol

75 of 454

12C07.2

CV 2

Ammonia

76 of 454

Ammonia

Liquid NH₃

N₂ + H₂

H₂

N₂

At 700 K

Born – Haber Process

High pressure favors ammonia formation

Optimum Conditions – 200 atm pressure

77 of 454

Ammonia

Present in air and soil

Decay of nitrogenous organic matter

NH₂CONH₂ + 2H₂O (NH₄)₂CO₃ ⇌ 2NH₃ + H₂O + CO₂

Decomposition of ammonium salts

2NH₄Cl + Ca(OH)₂ 2NH₃ + 2H₂O + CaCl₂

(NH₄)₂SO₄ + 2NaOH 2NH₃ + 2H₂O + Na₂SO₄

By Lime soda and caustic soda

78 of 454

Ammonia

Ammonia (NH₃)

Physical Properties

Colorless gas & Pungent odour

Freezing point and boiling point 198.4 and 239.7 k

Geometry and shape

sp³

Tetrahedral - GEOMETRY

Trigonal pyramidal - SHAPE

Bond Length – 101.7 pm

Bond angle – 107.8^o

79 of 454

Ammonia

Ammonia (NH₃)

Physical Properties

High melting point and boiling point

Highly soluble in water

+δ

�

+δ

�

+δ

�

+δ

�

+δ

�

-δ

�

-δ

�

Aqueous solution is weakly basic due to OH^- ions

NH₃(g) + H₂O(l) NH₄⁺(aq) + OH^-(aq)

80 of 454

Ammonia

Ammonia (NH₃)

Chemical Properties

Forms ammonium salts with acids

ZnSO₄(aq) + 2NH₄OH(aq) Zn(OH)₂(s) + (NH₄)₂SO₄(aq)

White ppt

FeCl₃(aq) + NH₄OH(aq) Fe₂O₃ . x H₂O(s) + NH₄Cl(aq)

Brown ppt

Role as Lewis base

Lone pair of electrons can be easily donated

Thus form linkage with metal ions like Cu²⁺ , Ag⁺

Thus help in detection of metal ions like Cu²⁺ , Ag⁺

81 of 454

Ammonia

Ammonia (NH₃)

Chemical Properties

Reaction with Ag⁺ and Cu²⁺

Ag⁺(aq) + Cl^-(aq) AgCl(s)

White ppt

AgCl(s) + 2NH₃(aq) [Ag(NH₃)₂ ]Cl(aq)

Colorless

Deep blue

82 of 454

Ammonia

Ammonia (NH₃)

Nitrogeneous fertilisers

Refrigerant

Manufacturing of some important inorganic compounds

Manufacturing of Nitric acid through Ostwald process

83 of 454

Q. Mention the conditions required to maximize yield of ammonia.

Pause the video

Time duration - 2 min

NCERT, Exercise Question – 7.4

Page no. – 177

84 of 454

Q. Mention the conditions required to maximize yield of ammonia.

Sol.

According to Lechatelier’s principle

For exothermic reaction , Temperature

Forward Reaction

But temperature should not be too low otherwise reaction will not start

For less number of moles of product,

Increase in pressure will lead to forward reaction

Optimum conditions – 700 K temperature

200 atm pressure

85 of 454

12C07.2

CV3

Oxides of Nitrogen

86 of 454

Oxides of nitrogen

Dinitrogen oxide

N₂O

Preparation - NH₄NO₃ N ₂O + 2H₂O

Heat

Oxidation state = +1

Colorless gas with neutral nature

N N O

113 pm 119pm

Resonance structure

Bond Parameter

Linear shape

87 of 454

Oxides of nitrogen

Nitrogen monoxide

Preparation – 2 NaNO₂ + 2FeSO₄+ 3H₂SO₄ Fe₂(SO₄)₃+ 2NaHSO₄ + 2H₂O + 2NO

Oxidation state = +2

Colorless gas with neutral nature

N O

115 pm

Resonance structure

Bond Parameter

Linear shape

88 of 454

Oxides of nitrogen

Dinitrogen trioxide

N₂O₃

Preparation – 2NO + N₂O₄ 2N ₂O₃

250 K

Oxidation state = +3

Blue solid with acidic nature

Resonance structure

Bond Parameter

Planar shape

89 of 454

Oxides of nitrogen

Nitrogen dioxide

NO₂

Preparation – 2Pb(NO₃)₂ 4N O₂ + 2PbO + O₂

673 K

Oxidation state = +4

Brown gas with acidic nature

Resonance structure

Bond Parameter

Angular shape

Paramagnetic [1 unpaired electron]

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Oxides of nitrogen

Dinitrogen tetraoxide

N₂O₄

Preparation – 2NO₂N ₂ O₄

Cool

Oxidation state = +4

Colorless solid/liquid with acidic nature

Resonance structure

Bond Parameter

Planar shape

Heat

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Oxides of nitrogen

Dinitrogen pentoxide

N₂O₅

Preparation – 4HNO₃ + P₄O₁₀ 4HPO₃ + 2N ₂O₅

Oxidation state = +5

Colorless solid with acidic nature

Resonance structure

Bond Parameter

92 of 454

Q. What is covalence of N in N₂O₅ ?

Pause the video

Time duration - 2 min

NCERT, Intext Question – 7.6

Page no. – 179

93 of 454

Q. What is covalence of N in N₂O₅ ?

Sol.

Covalency – Number of bonds formed by atom

Each N is forming 4 bonds

Covalence of N = 4

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PSV 01

12C07.2

95 of 454

Q. Why does NO₂ dimerise?

Pause the video

Time duration - 2 min

NCERT, Example Question – 7.5

Page no. – 179

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Q. Why does NO₂ dimerise?

Sol.

Unpaired electron

Odd molecule

Even molecule

Even number of electron

Odd molecule always dimerise to form even molecule

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12C07.2

CV 4

Nitric acid

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Oxoacids of Nitrogen

H₂N₂O₂

Hyponitrous acid

HNO₃

Most important

HNO₂

Nitrous acid

Preparation of HNO₃

Nitric acid

Glass retort

Sodium nitrate + conc. H₂SO₄

Brown fumes

NaNO₃ + H₂SO₄ NaHSO₄ + HNO₃

KNO₃ can also be used

Nitric acid

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Nitric acid

Ostwald’s process

Waste gas

Quartz pieces

Nitric acid

NH₃ + O₂

Converter

Oxidation

chamber

Absorption

tower

Pt gauze

Catalytic oxidation – 4NH₃(g) + 5O₂(g) 4NO(g) + 6H₂O(g)

Oxidation chamber – 2NO(g) + O₂(g) ⇌ 2NO₂(g)

Absorption tower – 3NO₂(g) + H₂O(l) 2HNO₃(aq) + NO(g)

Pt/Rh gauge catalyst

500 K, 9 bar

NO formed is recycled

Aq HNO₃ can be concentrated by distillation upto 68% by mass

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Nitric acid

Properties of HNO₃

Physical Properties

Colorless liquid

Freezing point – 231.4 K

Boiling point – 355.6 K

Laboratory grade – 68% HNO₃ by mass with specific gravity 1.504

PLANAR SHAPE

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Nitric acid

Properties of HNO₃

Chemical Properties

Aqueous solution is acidic

Action of concentrated and dilute HNO₃ on metals

8HNO₃ (dilute) + 3Cu 4H₂O + 3Cu(NO₃)₂ + 2NO

4HNO₃ (conc.) + Cu 2H₂O + Cu(NO₃)₂ + 2NO₂

Oxidation of Cu takes place from 0 to +2 O.S by HNO₃

10HNO₃ (dilute) + 4Zn 5H₂O + 4Zn(NO₃)₂ + N₂O

4HNO₃ (conc.) + Zn 2H₂O + Zn(NO₃)₂ + 2NO₂

+5 Oxidation state of N in HNO₃ makes it an oxidizing agent

HNO₃ does not attack noble metals like Au and Pt

Conc. HNO₃ does not attack metals like Cr, Al due to passive film of oxide

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Nitric acid

Properties of HNO₃

Chemical Properties

Oxidation of non metals and their compounds

Carbon to carbondioxide

I₂ + 10HNO₃ 2HIO₃ + 10NO₂ + 4H₂O

C + 4HNO₃ CO₂ + 4NO₂ + 2H₂O

Iodine to iodic acid

Sulphur to sulphuric acid

S₈ + 48HNO₃ 8H₂SO₄ + 48NO₂ + 16H₂O

Phosphorus to phosphoric acid

P₄ + 20HNO₃ 4H₃PO₄ + 20NO₂ + 4H₂O

Oxidation from 0 to +5 of iodine

Oxidation from 0 to +4 of carbon

Oxidation from 0 to +6 of sulphur

Oxidation from 0 to +5 of nitrogen

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Brown Ring Test

Aq. Sol. of nitrate

Adding Fe₂SO₄

To nitrate sol.

Sol. of Fe₂SO₄

Adding conc. H₂SO₄

To sol. drop by drop

Formation of brown ring

NO₃^- + 3Fe²⁺ + 4 H⁺ NO + 3Fe³⁺ + 2H₂O

[ Fe(H₂O)₅]²⁺ + NO [ Fe(H₂O)₅ NO ]²⁺ + H₂O

Brown ring

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Uses of Nitric acid

Uses of HNO₃

Manufacturing of ammonium nitrate which is used as fertilizer

Preparation of explosives

Trinitrotoluene

Nitroglycerine

Pickling of stainless steel

Etching of metals

Oxidiser in rocket fuels

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12C07.2

CV 5

Phosphine

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Allotropes of phosphorus

Allotropic forms of phosphorus

Black Phosphorus

Reaction with NaOH

White Phosphorus

Red Phosphorus

P₄ + 3NaOH + 3 H₂O PH₃ + 3NaH₂PO₂

Stability

P₄ + 5O₂ P₄O₁₀

Less stable and more reactive than other forms due to angular strain

Readily catches fire in air

Angular strain

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Red Phosphorus

Non Poisonous iron grey solid

Insoluble in water & CS₂

Does not glow in dark

Odourless

White Phosphorus

Red Phosphorus

573 K, Inert

atmosphere

Several days

High Pressure

Black Phosphorus

Structure

P₄ tetrahedral link together to form polymeric structure

Less reactive than

white phosphorus

Allotropes of phosphorus

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Black Phosphorus

α – Black phosphorus

β – Black phosphorus

Red Phosphorus

803 K, Sealed

tube

α – Black phosphorus

White Phosphorus

473 K, high pressure

β – Black phosphorus

Does not conduct electricity
Can be sublimed in air
Opaque monoclinic or rhombohedral crystal

Conduct electricity
Does not burn in air upto 673 K

Allotropes of phosphorus

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Phosphine

Preparation of PH₃

By Calcium phosphide

By White phosphorus

Ca₃P₂ + 6H₂O 3Ca(OH)₂ + 2PH₃

Ca₃P₂ + 6HCl 3CaCl₂ + 2PH₃

Heating white phosphorus with concentrated NaOH

P₄ + 3NaOH + 3H₂O 3NaH₂PO₂ + PH₃

Sodium hypophosphite

Flammable due to the presence of P₄ or P₂H₄ vapours

Purifying from its impurities - PH₃ + HI PH₄I

PH₄I + KOH KI + PH₃ + H₂O

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Phosphine

Properties of PH₃

Physical Properties

Chemical Properties

Colorless gas with rotten fish smell
Highly poisonous
Explodes in contact with traces of oxidizing agents like HNO₃, Cl₂ & Br₂ vapours
Slightly soluble in water

Solution with water

PH₃ Red Phosphorus + H₂

hν, water

Formation of phosphides

3CuSO₄ + 2PH₃ Cu₃P₂ + 3H₂SO₄

3HgCl₂ + 2PH₃ Hg₃P₂ + 6HCl

Phosphonium compounds

PH₃ + HBr PH₄Br

Acting as

base

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Phosphine

Uses of PH₃

Holme’s signal

Container containing calcium carbide and calcium phosphide are pierced and thrown in sea

PH₃ also used in smoke screens

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Q. In what way, it can be proved that PH₃ is basic ?

Pause the video

Time duration - 2 min

NCERT, Example Question – 7.6

Page no. – 182

113 of 454

Q. In what way, it can be proved that PH₃ is basic ?

Sol.

These lone pair can be donated

and thus can act as lewis base

Basic nature can be shown on reaction with acid

PH₃ + HI PH₄I

Acid

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PSV 02

12C07.2

115 of 454

Q. Write the main difference between white phosphorus and red phosphorus.

Pause the video

Time duration - 2 min

NCERT, Exercise Question – 7.13

Page no. – 213

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Q. Write the main difference between white phosphorus and red phosphorus.

Sol.

White Phosphorus	Red Phosphorus
Soft Translucent waxy solid	Hard crystalline Red solid

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Q. Write the main difference between white phosphorus and red phosphorus.

Sol.

White Phosphorus	Red Phosphorus
Soft Translucent waxy solid	Hard crystalline Red solid
Garlic like odour	Odourless

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Q. Write the main difference between white phosphorus and red phosphorus.

Sol.

White Phosphorus	Red Phosphorus
Soft Translucent waxy solid	Hard crystalline Red solid
Garlic like odour	Odourless
Poisonous	Non - poisonous

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Q. Write the main difference between white phosphorus and red phosphorus.

Sol.

White Phosphorus	Red Phosphorus
Soft Translucent waxy solid	Hard crystalline Red solid
Garlic like odour	Odourless
Poisonous	Non - poisonous

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Q. Write the main difference between white phosphorus and red phosphorus.

Sol.

White Phosphorus	Red Phosphorus
Soft Translucent waxy solid	Hard crystalline Red solid
Garlic like odour	Odourless
Poisonous	Non - poisonous

	Exist as polymeric network

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Q. Write the main difference between white phosphorus and red phosphorus.

Sol.

White Phosphorus	Red Phosphorus
Soft Translucent waxy solid	Hard crystalline Red solid
Garlic like odour	Odourless
Poisonous	Non - poisonous

	Exist as polymeric network
Waxy solid which when exposed to light becomes yellow	Appears as dark red crystals

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Q. Write the main difference between white phosphorus and red phosphorus.

Sol.

White Phosphorus	Red Phosphorus
Soft Translucent waxy solid	Hard crystalline Red solid
Garlic like odour	Odourless
Poisonous	Non - poisonous

	Exist as polymeric network
Waxy solid which when exposed to light becomes yellow	Appears as dark red crystals
Ignites in air at low temperature at approx. 50^o C	Ignites in air at high temperature, approx. 240^o C

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Q. Write the main difference between white phosphorus and red phosphorus.

Sol.

White Phosphorus	Red Phosphorus
Soft Translucent waxy solid	Hard crystalline Red solid
Garlic like odour	Odourless
Poisonous	Non - poisonous

	Exist as polymeric network
Waxy solid which when exposed to light becomes yellow	Appears as dark red crystals
Ignites in air at low temperature at approx. 50^o C	Ignites in air at high temperature, approx. 240^o C
Angle strain is present thus more reactive and less stable	No angle strain

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12C07.2

CV 6

Phosphorus Halides

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Phosphorus halides

Phosphorus Halides

PX₃

PX₅

Phosphorus Trichloride PCl₃

Preparation

Passing dry chlorine over heated white phosphorus

P₄ + 6Cl₂ 4PCl₃

Action of thionyl Chloride

P₄ + 8SOCl₂ 4PCl₃ + 4SO₂ + 2S₂Cl₂

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Phosphorus halides

Phosphorus Trichloride PCl₃

Properties

Physical Properties

Chemical Properties

sp³

Colorless oily liquid

Pyramidal shape

Reaction with water

PCl₃ + 3H₂O H₃PO₃ + 3HCl

Reaction with compounds containing OH group

PCl₃ + 3CH₃COOH H₃PO₃ + 3CH₃COCl

PCl₃ + 3C₂H₅OH H₃PO₃ + 3C₂H₅Cl

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Phosphorus halides

Phosphorus Pentachloride PCl₅

Preparation

Passing excess dry chlorine over heated white phosphorus

P₄ + 10Cl₂ 4PCl₅

Action of thionyl Chloride

P₄ + 10SOCl₂ 4PCl₅ + 10SO₂

Properties

Physical Properties

sp³d

Trigonal bipyramidal geometry

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Phosphorus halides

Properties

Chemical Properties

Hydrolysis of PCl₅

PCl₅ + H₂O POCl₃ + 2HCl

POCl₃ + 3H₂O H₃PO₄ + 3HCl

Decomposition of PCl₅

PCl₅ PCl₃ + Cl₂

Action on Organic compound

PCl₅ + CH₃COOH POCl₃ + CH₃COCl + HCl

PCl₅ + C₂H₅OH POCl₃ + C₂H₅Cl + HCl

Action on metals

2Ag + PCl₅ PCl₃ + 2AgCl

Sn + PCl₅ 2PCl₃ + SnCl₄

More repulsion in bond pairs

Less repulsion in bond pairs

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Q. What happens when PCl₅ is heated ? What happens when it react with water ?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.9, 7.10

Page no. 184

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Q. What happens when PCl₅ is heated ? What happens when it react with water ?

Sol.

Longer bonds can easily be broken

Thus on heating, PCl₅ PCl₃ + Cl₂

Reaction with water

PCl₅ + H₂O POCl₃ + 2 HCl

POCl₃ + 3H₂O H₃PO₄ + 3HCl

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ConcepTest

Ready for challenge

132 of 454

Q. Can PCl₅ act as reducing agent as well as oxidizing agent ?

Pause the video

Time duration - 2 min

NCERT, Exercise question – 7.16

Page no. 213

133 of 454

Sol.

Q. Can PCl₅ act as reducing agent as well as oxidizing agent ?

Reducing agent – One which oxidises itself but reduces others

Oxidising agent – One which reduces itself but oxidises others

Oxidation state = + 5

Highest oxidation state

Of group 15 elements

Reducing agent – P will have to oxidise itself but P can’t go above +5

Thus PCl₅ can act as oxidizing agent

Oxidizing agent – P will have to reduce itself as P is in max. O.S (+5 )

P can easily reduce itself by decreasing its O.S

Thus PCl₅ can’t act as reducing agent

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12C07.2

CV 7

Oxoacids of phosphorus

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Oxoacids of phosphorus

Hypophosphorus ( Phosphinic )

H₃PO₂

1 P = O

1 P – OH

2 P – H

2 P – H bonds thus a Good reducing agent

Example – Reduction of Ag

4AgNO₃ + 2H₂O + H₃PO₂ 4Ag + 4HNO₃ + H₃PO₄

O.S is +1

Preparation – white P₄ + alkali

Not ionisable to give H⁺

Monobasic because only 1 H⁺ is ionizable

An acid which contains a.) oxygen b.) at least one other element d.) has at least one H atom bounded to O e.) Can release at least one H⁺ to show its acidic character

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Orthophosphorus ( Phosphonic )

H₃PO₃

1 P = O

2 P – OH

1 P – H

O.S is +3

Preparation – P₂O₃ + H₂O

Not ionisable to give H⁺

Dibasic because only 2 H⁺ is ionizable

Pyrophosphorus

H₄P₂O₅

2 P = O

2 P – OH

2 P – H

1 P – O – P

O.S is +3

Preparation – PCl₃ + H₃PO₃

Dibasic because only 2 H⁺ is ionizable

Oxoacids of phosphorus

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Hypophosphoric

H₄P₂O₆

2 P = O

4 P – OH

1 P – P

Tetrabasic because only 4 H⁺ is ionizable

Preparation – red P₄ + alkali

Orthophosphoric

H₄PO₄

1 P = O

3 P – OH

O.S is +5

Tribasic because only 3 H⁺ is ionizable

Preparation – P₄O₁₀ + H₂O

Oxoacids of phosphorus

O.S is +4

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Pyrophosphoric

H₄P₂O₇

2 P = O

4 P – OH

1 P – O – P

O.S is +5

Preparation – Heating H₃PO₄

Tetrabasic because only 4 H⁺ is ionizable

Metaphosphoric

(HPO₃)_n

Preparation – Heating H₃PO₃ + Br₂ in sealed tube

Oxoacids of phosphorus

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Metaphosphoric

(HPO₃)_n

Polymetaphosphoric acid

(HPO₃)₃

Cyclometaphosphoric acid

3 P = O

3 P – OH

3 P – O – P

Oxoacids of phosphorus

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Q. What is the basicity of H₃PO₄ ?

Pause the video

Time duration - 2 min

NCERT, Exercise question – 7.11

Page no. 185

141 of 454

Q. What is the basicity of H₃PO₄ ?

Bascity of H₃PO₄ – Number of replaceable hydrogen atoms in one molecule of acid

Sol. H attached to electronegative atom can be lost as H⁺

3 replaceable hydrogen

Basicity = 3

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Summary

Preparation of N₂

NH₄Cl (aq) + NaNO₂ (aq) N₂ (g) + 2H₂O (l) + NaCl (aq)

6Li + N₂ 2Li₃N

Heat

N₂ (g) + 3H₂ (g) 2NH₃ (g)

⇌

N₂ + O₂ 2NO

⇌

N₂

Preparation of NH₃

N₂ (g) + 3H₂ (g) 2NH₃ (g)

⇌

ZnSO₄(aq) + 2NH₄OH(aq) Zn(OH)₂(s) + (NH₄)₂SO₄(aq)

Properties of NH₃

Cu²⁺ + 4NH₃(aq) [Cu(NH₃)₄ ]²⁺(aq)

Preparation of HNO₃

Ostwald’s process

Properties of HNO₃

Properties PH₃

3CuSO₄ + 2PH₃ Cu₃P₂ + 3H₂SO₄

PH₃ + HBr PH₄Br

PH₃ Red Phosphorus + H₂

hν, water

Properties PCl₃

PCl₃ + 3H₂O H₃PO₃ + 3HCl

PCl₃ + 3CH₃COOH H₃PO₃ + 3CH₃COCl

PCl₃ + 3C₂H₅OH H₃PO₃ + 3C₂H₅Cl

Properties PCl₅

PCl₅ + H₂O POCl₃ + 2HCl

POCl₃ + 3H₂O H₃PO₄ + 3HCl

PCl₅ PCl₃ + Cl₂

2Ag + PCl₅ PCl₃ + 2AgCl

–

Dilute HNO₃ with Cu & Zn form NO and N₂O respectively.

Concentrated HNO₃ with Cu & Zn form NO₂ in both cases.

–

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Reference Questions

Intext Question, NCERT : 7.5, Page no. – 177

7.8, Page no. – 182

7.11, Page no. – 185

Example Question, NCERT : 7.4, Page no. – 177

7.7, Page no. – 183

7.8, Page no. – 183

7.9, Page no. – 185

Exercise Question, NCERT : 7.2, Page no. – 213

7.4, Page no. – 213

7.5, Page no. – 213

7.12, Page no. – 213

7.14, Page no. – 213

Workbook Questions: 4, 5,13, 14, 15, 16,17,18,19, 20

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12C07.3��General concepts about group 16 elements��

145 of 454

��12C07.3 General Concepts about group 16 elements��

Learning Objectives

Basic Concepts of group 16 elements

Physical properties of group 16 elements

Chemical properties of group 16 elements

Anomalous behavior of oxygen

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12C07.3

CV 1

Basic Concepts of group 16 elements

147 of 454

��Basic Concepts about group 16 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Oxygen	O	8	16	Non metal
Sulphur	S	16	32.06	Non metal
Selenium	Se	34	78.96	Metalloid
Tellurium	Te	52	127.60	Metalloid
Polonium	Po	84	210	Metal

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��Basic Concepts about group 16 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Oxygen	O	8	16	Non metal
Sulphur	S	16	32.06	Non metal
Selenium	Se	34	78.96	Metalloid
Tellurium	Te	52	127.60	Metalloid
Polonium	Po	84	210	Metal

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��Basic Concepts about group 16 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Oxygen	O	8	16	Non metal
Sulphur	S	16	32.06	Non metal
Selenium	Se	34	78.96	Metalloid
Tellurium	Te	52	127.60	Metalloid
Polonium	Po	84	210	Metal

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��Basic Concepts about group 16 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Oxygen	O	8	16	Non metal
Sulphur	S	16	32.06	Non metal
Selenium	Se	34	78.96	Metalloid
Tellurium	Te	52	127.60	Metalloid
Polonium	Po	84	210	Metal

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��Basic Concepts about group 16 elements��

Name of element	Symbol of element	Atomic Number	Atomic mass (g/mol)	Characteristic
Oxygen	O	8	16	Non metal
Sulphur	S	16	32.06	Non metal
Selenium	Se	34	78.96	Metalloid
Tellurium	Te	52	127.60	Metalloid
Polonium	Po	84	210	Metal

General Electronic Configuration – ns²np⁴

Also called chalcogens

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Occurrence of group 16 elements

Oxygen

O₂ 21% by volume

O about 46.6% by mass of earth crust

Most abundant of all elements

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Occurrence of group 16 elements

Sulphur

S about 0.03 – 0.1% earth crust

Sulphide

Organic materials

Sulphates

Gypsum – CaSO₄. 2 H₂O

Epsom Salt – MgSO₄. 7 H₂O

Baryte – BaSO₄

PbS Galena

ZnS Zinc Blende

CuFeS₂ Copper pyrite

H₂S in volcanoes

Also found in proteins

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Occurrence of group 16 elements

Selenium and tellurium

Selenides sulphide ore

Cu₂SnS₄

Occurs as decay product of thorium and uranium minerals

Bi₂Te₂S

Polonium

Tellurides sulphide ore

Livermonium

Symbol Lv

Atomic mass =292 g/mol

Atomic number = 116

[Rn] 5f¹⁴6d¹⁰ 7s² 7p⁴

Radioactive

Half life of only small fraction of second

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12C07.3

CV 2

Physical Properties of group 16 elements

156 of 454

Name of element	Symbol of element	Electronic configuration
Oxygen	O	[He]2s²2p⁴
Sulphur	S	[Ne]3s²3p⁴
Selenium	Se	[Ar]3d¹⁰4s²4p⁴
Tellurium	Te	[Kr]4d¹⁰5s²5p⁴
Polonium	Po	[Xe]4f¹⁴5d¹⁰6s²6p⁴

Filled inner d orbitals

d-orbitals not present

Electronic configuration of group 16 elements

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Trends in various physical properties

Atomic and ionic radii

Number

of shells

increase

Atomic size

increase

Symbol of element	Covalent radii (pm)	Electronic configuration
O	66	[He]2s²2p⁴
S	104	[Ne]3s²3p⁴
Se	117	[Ar]3d¹⁰4s²4p⁴
Te	137	[Kr]4d¹⁰5s²5p⁴
Po	146	[Xe]4f¹⁴5d¹⁰6s²6p⁴

O has exceptionally small radius

Trends in Physical Properties of group 16 elements

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Symbol of element	Ionization energy (kJ/mol)
O	1314
S	1000
Se	941
Te	869
Po	813

Ionization Enthalpy

Ionization

Enthalpy

decrease

Atomic radii

increase

Nucleus attraction

towards valence e^–

decrease

NOTE – ΔH₁<< ΔH₂

Ionization enthalpy smaller than group 15 element due to extra stable half filled configuration of group 15 elements which require extra energy to remove electron

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Symbol of element	Electron gain enthalpy (kJ/mol)
O	-141
S	-200
Se	-195
Te	-190
Po	-174

Electron gain enthalpy

decrease

Atomic radii

increase

Nucleus attraction

towards valence e^– decrease

Electron gain enthalpy larger than group 15 element due to small size of gp 16 elements and high effective nuclear charge

S has more enthalpy than O because O has extremely small size

which causes repulsion between electrons

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Symbol of element	Electronegativity
O	3.5
S	2.58
Se	2.55
Te	2.01
Po	1.76

Electronegativity

Atomic radii

increase

Nucleus attraction

towards valence e^- decrease

Electronegativity

decrease

Greater than group 15 elements due to greater effective nuclear charge of group 16 elements

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Symbol of element	M.P/K	B.P/K
O	55	90
S	393	718
Se	490	958
Te	725	1260
Po	520	1235

Atomic mass

increase

Boiling point

increase

Large difference between O and S

Melting point and boiling point

Melting point

increase

O exist as O₂ and S exist as S₈

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Metallic and non-metallic character

Atomic radii

increase

Ionization enthalpy

decrease

Metallic character

increase

Name of element	Symbol of element
Oxygen	O
Sulphur	S
Selenium	Se
Tellurium	Te
Polonium	Po

Characteristic
Non metal
Non metal
Metalloid
Metalloid
Metal

163 of 454

ConcepTest

Ready for challenge

164 of 454

Q. Knowing the electron gain enthalpy values for O – O^- and O – O^2- as -141 and 702 kJ/mol respectively, how can

you account for the formation of a large number of oxides having O^2- species and not O^-?

Pause the video

Time duration - 2 min

NCERT, Exercise question – 7.19

Page no. 213

165 of 454

Q. Knowing the electron gain enthalpy values for O – O^- and O – O^2- as -141 and 702 kJ/mol respectively, how can

you account for the formation of a large number of oxides having O^2- species and not O^- ?

Sol.

Formation of compounds depend on lattice energy

If Lattice energy

Stable compound is formed

CHARGE - O^2- > O^-

Lattice energy for O^2- > Lattice energy for O^-1

Thus more number of oxides with O^2- are formed than oxides with O^-1

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12C07.3

CV 3

Chemical Properties of group 16 elements

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Oxidation state of group 16 elements

Symbol of element	Oxidation state
O	-1,-2, +2
S	-2, +2, +4, +6
Se	-2, +2, +4, +6
Te	+2, +4, +6
Po	+2, +4

Maximum covalency is 3

Common Oxidation state (O.S) is +4, +6

+2 O.S with only OF₂

+6 O.S with fluorine

+4 O.S with oxygen

168 of 454

Oxidation state of group 16 elements

Symbol of element	Oxidation state
O	-2, +2, -1
S	-2, +2, +4, +6
Se	-2, +2, +4, +6
Te	+2, +4, +6
Po	+2, +4

Common Oxidation state (O.S) is +4, +6

Stability of -2 decreases

Stability of +6 decreases

Stability of +4 increases

Bonding in +4 & +6 O.S is primarily covalent

169 of 454

Oxidation state of group 16 elements

Inert Pair effect

No. of shells

increase

Addition of d and f electron

increase

Ineffective shielders of valence electron

Stability

Of +6 O.S

decrease

Symbol of element	Oxidation state
O	-2, +2, -1
S	-2, +2, +4, +6
Se	-2, +2, +4, +6
Te	+2, +4, +6
Po	+2, +4

170 of 454

Reactions of group 16 elements

Reaction with hydrogen

Reaction with halogen

Reaction with Oxygen

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Reactions of group 16 elements

Reaction with hydrogen

H₂E type hydrides are formed [ E = 16 group elements]

Order of stability of hydrides

THERMAL STABILITY ORDER : H₂O> H₂S>H₂Se >H₂Te> H₂Po

2p – 1s

3p – 1s

4p – 1s

5p – 1s

OVERLAPPING ORDER : 2p – 1s > 3p – 1s > 4p – 1s > 5p – 1s

Bond dissociation enthalpy : H₂O> H₂S>H₂Se >H₂Te> H₂Po

172 of 454

Reactions of group 16 elements

Reaction with hydrogen

H₂E type hydrides are formed [ E = 15 group elements]

Reducing and acidic character of Hydrides

BOND LENGTH : H₂O< H₂S< H₂Se<H₂Te<H₂Po

Reducing nature: H₂O< H₂S< H₂Se<H₂Te<H₂Po

Acidic character : H₂O< H₂S< H₂Se<H₂Te<H₂Po

No reducing property

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Reactions of group 16 elements

Reaction with Oxygen

EO₂ & EO₃ type [E is element]

EO₃ more acidic than EO₂ as element is in +6 O.S so more electron deficient than +4 O.S thus EO₃ act as stronger lewis acid

O₃	SO₂	SeO₂	TeO₂

Reducing character

decreases

Symbol of element
O
S
Se
Te

Stability of +6 O.S decreases

EO₂ & EO₃ both are acidic oxides

Gases

Solid

TeO₂ is an oxidising agent while SO₂ is a reducing agent

O.S of Te and S is +4.

Reducing agent – one who get oxidized and S can go from +4 to +6 while Te can’t go from +4 to +6 due to inert pair effect

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Reactions of group 16 elements

Reaction with halogen

EX₆, EX₄ & EX₂ type [X is halogen]

Stability of halides

F^- > Cl^- > Br ^- > I^-

Among hexahalides, Hexafluorides are the most stable halides

Hexafluorides are gaseous in nature

SF₆ is exceptionally stable due to steric reasons

SF₄	SeF₄	TeF₄

Gas

Liquid

Solid

sp³d hybridization

Trigonal bipyramidal - geometry

See – saw shape

sp³d² hybridization

Octahedral - geometry

EX₄ Type

EX₆ Type

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Reactions of group 16 elements

Reaction with halogen

EX₆, EX₄ & EX₂ type [X is halogen]

EX₂ Type

All elements except oxygen form dichloride and dibromide

Repulsion between

two Cl atoms

Repulsion between

two Br atoms

sp³ hybridization

Tetrahedral – geometry

Dimeric Nature

Example – S₂F₂, S₂Cl₂ , S₂Br₂ , Se₂Cl₂ , Se₂Br₂

Disproportionation – 2 Se₂Cl₂ SeCl₄ + 3 Se

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PSV 01

12C07.3

177 of 454

Q. Why SF₄ can be hydrolysed whereas SF₆ cannot be hydrolysed?

Pause the video

Time duration - 2 min

Workbook Question – 6

178 of 454

Q. Why SF₄ can be hydrolysed whereas SF₆ cannot be hydrolysed?

Lone pair of electrons occupied

equatorial bond

Sol.

No bond is vacant. Sulphur is

overcrowded with F

H₂O

Because one bond is vacant

Thus, SF₄ can easily be hydrolysed

There is no gap for H₂O to attack

Thus, SF₆ can’t be hydrolysed

179 of 454

12C07.3

CV 4

Anomalous behavior of oxygen

180 of 454

Anomalous behavior of O

Anomalous Behavior of oxygen

Due to characteristics of O

ExtremelySmall size

Attraction of electrons due

to high electronegativity of O

High ionization energy

No d orbital

181 of 454

Anomalous Behavior of oxygen

Ability to form hydrogen bonding

+δ

�

-δ

�

+δ

�

+δ

�

+δ

�

-δ

�

-δ

�

-δ

�

+δ

�

+δ

�

+δ

�

+δ

�

Small size and high electronegativity enables Hydrogen bonding

Large size and less electronegativity does not enable Hydrogen bonding

Anomalous behavior of O

182 of 454

Anomalous Behavior of oxygen

Ability to form pπ – pπ multiple bond

Small size makes formation of multiple bond easier

Inability to expand covalency

2p⁴

2s²

Maximum covalency = 3

Anomalous behavior of O

π Overlap

σ Overlap

183 of 454

Q. Why H₂O is liquid whereas H₂S is gas ?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.15

Page no. 189

184 of 454

Q. Why H₂O is liquid whereas H₂S is gas ?

Sol.

+δ

�

-δ

�

+δ

�

+δ

�

+δ

�

-δ

�

-δ

�

-δ

�

+δ

�

+δ

�

+δ

�

+δ

�

Intermolecular force is

Hydrogen Bonding which is

Possible due to small size

and high electronegativity

of oxygen

Hydrogen Bonding is not

possible due to large size

and low electronegativity of S

Vanderwaal forces exist

Vanderwaal forces are weaker than hydrogen bonding

Thus H₂O is liquid whereas H₂S is gas

185 of 454

Summary

1.) General electronic configuration of group 15 elements is ns²np³

I.E

decrease

Electron gain

enthalpy

Dec.

Metallic

Character inc.

Atomic

radii inc.

B.P

inc.

2.) Common oxidation states are +4, +6

3.) These elements react with hydrogen to form hydrides of H₂E type.

4.) These elements react with oxygen to form oxides of EO₂ & EO₃ type.

Stability Of

+6 O.S dec.

5.) These elements react with halogen to form halides of EX₆ , EX₄ & EX₂ type.

Name of element	Symbol of element	Electronic configuration
Oxygen	O	[He]2s²2p⁴
Sulphur	S	[Ne]3s²3p⁴
Selenium	Se	[Ar]3d¹⁰4s²4p⁴
Tellurium	Te	[Kr]4d¹⁰5s²5p⁴
Polonium	Po	[Xe]4f¹⁴5d¹⁰6s²6p⁴

Electro

negativity

decrease

186 of 454

Reference Questions

Intext Question, NCERT : 7.13, Page no. – 189

7.14, Page no. – 189

Example Question, NCERT : 7.11, Page no. – 189

Exercise Question, NCERT : 7.17, Page no. – 213

187 of 454

12C07.4��Important compounds of group 16 elements��

188 of 454

��12C07.4 Important compounds of group 16 elements��

Learning Objectives

Dioxygen

Ozone

Sulphur dioxide

Oxoacids of sulphur

189 of 454

12C07.4

CV 1

Dioxygen

190 of 454

Dioxygen

Dioxygen (O₂)

Preparation of O₂

Fractional Distillation

Air Intake

Air heats up as it

is compressed

Liquid N₂

Compressed air is

cooled

Compressed air is

Allowed to expand and

Turn into liquid

Liquefied air in at -200^o C

Oxygen

Nitrogen

90 K

77.2 K

Compressor

191 of 454

Dioxygen (O₂)

Preparation of O₂

Heating Chlorates, nitrates and permanganates

2KClO₃ 2KCl + 3O₂

Thermal Decomposition of metal oxides which are low in electrochemical series

2Ag₂O 4Ag + O₂

2HgO 2Hg + O₂

2Pb₃O₄ 6PbO + O₂

2 PbO₂ 2PbO + O₂

Decomposition of H₂O₂ using catalyst MnO₂

2H₂O₂ 2H₂O + O₂

Dioxygen

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Dioxygen (O₂)

Preparation of O₂

Electrolysis of water

Electron flow

H₂

O₂

Pt electrodes

ANODE

2 H₂O(l) O₂(g) + 4 H⁺ + 4 e^-

Dioxygen

193 of 454

Dioxygen

Dioxygen (O₂)

Properties of O₂

Physical Properties

Colorless and odorless

Liquifies at 90 K & freezes at 55 K

Solubility in water is 3.08 cm³ in 100 cm³

�

Shape of O₂

Hybridization - sp²

Isotope of oxygen

¹⁷O

¹⁸O

¹⁶O

π Overlap

σ Overlap

194 of 454

Dioxygen

Dioxygen (O₂)

Properties of O₂

Paramagnetic nature of O₂

Unpaired electrons in antibonding orbitals

195 of 454

Dioxygen

Dioxygen (O₂)

Properties of O₂

Chemical Properties

Reaction with metals, non metals and some compounds

2Ca + O₂ 2CaO

2Al + 3O₂ 2Al₂O₃

P₄ + 5O₂ P₄O₁₀

C + O₂ CO₂

2ZnS + 3O₂ 2ZnO + 2SO₂

CH₄ + 2O₂ CO₂ + 2H₂O

Reaction with compounds using catalyst

2SO₂ + O₂ 2SO₃

4HCl + O₂ 2Cl₂ + 2H₂O

V₂O₅

CuCl₂

O₂ combination with most of the elements is exothermic

O=O bond dissociation enthalpy = 493.4 kJ/mol

Heat is required to initiate the reaction

196 of 454

Dioxygen

Dinitrogen (O₂)

Uses of O₂

Respiration

Oxyacetylene welding in manufacturing of metals

Use of O₂ with C₂H₂

Combustion

O₂ cylinders in -

Hospitals

High altitude flying

Mountaineering

Combustion of hydrazine in liquid O₂ provides thrust for rocket

197 of 454

Q. Why O₂ is gas whereas Sulphur exist as solid?

Pause the video

Time duration - 2 min

NCERT, Exercise question – 7.18

Page no. 213

198 of 454

Q. Why O₂ is gas whereas Sulphur exist as solid?

Sol.

�

2 atoms of oxygen

8 atoms of sulphur

More molecular mass

Less molecular mass

Vanderwaal force of Sulphur is greater than O₂

Thus S₈ forms more closed packing than O₂ and is solid whereas O₂is gas

199 of 454

PSV 01

12C07.4

200 of 454

Q. Which of the following does not react with O₂ – Zn, Pt, Ti, Fe and complete the following reactions –

C₂H₄ + O₂
4Al + 3 O₂

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.16, 7.17

Page no. 190

201 of 454

Q. Which of the following does not react with O₂ – Zn, Pt, Ti, Fe and complete the following reactions –

C₂H₄ + O₂
4Al + 3 O₂

Sol. Among Zn, Pt, Ti, Fe - Pt does not react with O₂

C₂H₄ + 3O₂ 2CO₂ + 2H₂O

(ii) 4Al + 3 O₂ 2 Al₂O₃

202 of 454

12C07.4

CV 2

Ozone

203 of 454

Types of oxides

Simple oxide nature

Oxides

Simple Oxides

Mixed Oxides

MgO, Al₂O₃

Pb₃O₄ , Fe₃O₄

Acidic

Amphoteric

Basic

Non metallic oxide

Metallic oxide

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Acidic oxide

Oxide on combining with water gives an acid

SO₂ + H₂O H₂SO₃

An Acid

Example – SO₂ , Cl₂O₇, CO₂, N₂O₅

General rule – non metals form ACIDIC oxide

Exception – Some metal in high O.S also form acidic oxide – Mn₂O₇, CrO₃, V₂O₅

Basic oxide

Oxide on combining with water gives a base

CaO + H₂O Ca(OH)₂

A base

Example – Na₂O , CaO, BaO

General rule – metals form BASIC oxide

Types of oxides

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Amphoteric oxide

Oxides which show both basic as well as acidic character

React with acids as well as alkalies

Al₂O₃(s) + 6 NaOH(aq) + 3H₂O(l) 2Na₃[Al(OH)₆](aq)

Neutral oxide

Oxides which are neither basic nor acidic

Examples – N₂O, CO, NO

Types of oxides

206 of 454

Ozone

Ozone (O₃)

Preparation of O₃

Ozononised oxygen

Dilute H₂SO₄

Dry O₂

10% conversion of oxygen to ozone

Silent Electric discharge

3O₂ 2O₃ ΔH^o (298 K) = +142 kJ mol ^-1

Endothermic process

Battery of ozoniser used to increase conversion & pure O₃ can be condensed in vessel surrounded by liquid O₂

207 of 454

Ozone

Ozone (O₃)

Properties of O₃

Physical Properties

Pale blue gas, dark blue liquid, violet black solid
B.P – 101.1 K, Allotropic form of O₂ , Too reactive
At height of 20 Km it is formed from O₂ with sunlight
Harmful if concentration rises above 100 ppm

208 of 454

Ozone

Ozone (O₃)

Properties of O₃

Decomposition of ozone

Oxidising agent

O₃ O₂ + O

Nascent Oxygen

Very reactive

PbS(s) + 4O₃(g) PbSO₄(s) + 4O₂(g)

Chemical Properties

ΔH = Negative as O₃ is unstable

ΔS = Positive

ΔG = ΔH - T ΔS

= Large Negative

Thus high concentration of O₃ is explosive

O.S of I changes from -1 to 0

O.S of S changes from -2 to +6

Strong oxidizing agent

209 of 454

Ozone

Ozone (O₃)

Properties of O₃

Chemical Properties

Combination with Nitrogen oxide

2 I ^- (aq) + H₂O(l) + O₃(g) 2 OH^- (aq) + O₂(g) + I₂(s)

O₃ react with KI solution buffered with borate buffer (pH =9.2)

Titrated with Na₂S₂O₃

Method of estimating

O₃

Quantitative analysis of O₃

NO(g) + O₃(g) O₂(g) + NO₂(g)

Potential source of nitrogen oxide which can deplete O₃ layer

Supersonic jet planes

Freons and CFC’s

210 of 454

Ozone

Ozone (O₃)

Uses of O₃

Disinfectant

Germicide

For sterilizing water

Bleaching

Oils

Ivory

Flour

Starch

Oxidising agent in manufacture of KMnO₄

211 of 454

ConcepTest

Ready for challenge

212 of 454

Q. How is O₃ estimated quantitatively ?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.19

Page no. 192

213 of 454

Q. How is O₃ estimated quantitatively ?

Sol.

KI solution

O₃

I₂ liberated

Titrated with Na₂S₂O₃

I₂ + 2Na₂S₂O₃ Na₂S₄O₆ + 2NaI

1 mole of ozone forms 1 mole of I₂

With titration amount of I₂ can be found

Amount of O₃ = Amount of I₂

214 of 454

12C07.4

CV 3

Sulphur dioxide

215 of 454

Allotropes of S

Allotropes of Sulphur

Rhombic Sulphur

Monoclinic Sulphur

α-sulphur

β-sulphur

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Allotropes of S

Allotropes of Sulphur

Rhombic Sulphur

Monoclinic Sulphur

α-sulphur

β-sulphur

M.P – 385.8 K , specific gravity – 2.06

Roll sulphur

α-sulphur

CS₂

Insoluble in water but dissolves in CS₂ & to some extent in benzene, ether, alcohol

M.P – 393 K ,

specific gravity – 1.98

Crust is formed

α-sulphur

β-sulphur

α-sulphur

β-sulphur

Transition T = 369 K = 96^o C

At 369 K or 96^o C both forms are stable

Two holes made in crust

Melting & cooling

& removing crust

Pouring out liquid

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Existing forms of Sulphur

S₈

S₆

Crown form of sulphur

Chair form of sulphur

At elevated temperature approx. 1000 K, S₂ form exist

Paramagnetic

218 of 454

Sulphur dioxide

Sulphur dioxide (SO₂)

Preparation of SO₂

Combination of S & O₂

SO₃^– (aq) + 2 H⁺ H₂O(l) + SO₂ (g)

Little amount of SO₃ is also formed

Dil. H₂SO₄

Sodium

sulphite

SO₂

S + O₂ SO₂

Laboratory preparation

Industrial preparation

4FeS₂(s) + 11O₂(g) 8SO₂ (g) + 2Fe₂O₃(s)

Produced as by-product of roasting

Gas after drying is liquefied & stored in gas cylinders

219 of 454

Sulphur dioxide

Sulphur dioxide (SO₂)

Properties of SO₂

Physical Properties

Colorless gas with pungent odour

Highly soluble in water

Liquifies at R.T, 2 atm, B.P – 263 K

sp² hybridization

Angular shape

Resonance structures

–

220 of 454

Sulphur dioxide

Sulphur dioxide (SO₂)

Properties of SO₂

Chemical Properties

Reaction with water

SO₂(g) + H₂O(l) H₂SO₃

Reaction with NaOH

SO₂ + 2 NaOH Na₂SO₃ + H₂O

Na₂SO₃ + H₂O + SO₂ 2NaHSO₃

SO₂ behave same as CO₂

Reaction with Cl₂ in presence of charcoal

SO₂(g) + Cl₂(g) SO₂Cl₂

Charcoal act as catalyst

Reaction with O₂

SO₂(g) + O₂(g) SO₃

V₂O₅

Action as reducing agent

SO₂ + 2Fe³⁺ + 2H₂O 2Fe²⁺ + SO₄^2- + 4H⁺

5SO₂ + 2MnO₄^- + 2H₂O 2Mn²⁺ + 5SO₄^2- + 4H⁺

Purple

Colorless

Discoloration is test for SO₂ gas

221 of 454

Sulphur dioxide

Sulphur dioxide (SO₂)

Refining petroleum

Uses of SO₂

Refining sugar

Bleaching of wool and silk

Anti – chlor, disinfectant & preservative

Liquid SO₂ as solvent

Manufacturing of H₂SO₄, NaHSO₃, Ca(HSO₃)₂

222 of 454

Q. Comment on the nature of two S – O bonds formed in SO₂ molecule. Are these two S – O equal ?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.21

Page no. 194

223 of 454

Q. Comment on the nature of two S – O bonds formed in SO₂ molecule. Are these two S – O equal ?

Sol.

Thus due to resonating structure

two S – O bonds are of equal

length

–

224 of 454

PSV 02

12C07.4

225 of 454

Q. How is presence of SO₂ detected ?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.22

Page no. 194

226 of 454

Q. How is presence of SO₂ detected ?

Sol.

Acidified KMnO₄

solution

SO₂ act as reducing agent

MnSO₄ solution

Change of color from pink to colorless

Conversion of Mn⁺⁷ to Mn⁺²

5SO₂ + 2MnO₄^- + 2H₂O 2Mn²⁺ + 5SO₄^2- + 4 H⁺

227 of 454

ConcepTest

Ready for challenge

228 of 454

Q. How is SO₂ an air pollutant ?

Pause the video

Time duration - 2 min

NCERT, Exercise question – 7.22

Page no. 213

229 of 454

Q. How is SO₂ an air pollutant ?

Sol.

Reaction in the atmosphere to form H₂SO₄ &HNO₃ with

H₂O molecules

SO₂

NO_x

Droplets of rain water

carrying H₂SO₄

and HNO₃

230 of 454

12C07.4

CV 4

Oxoacids of sulphur

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Oxoacids of sulphur

Sulphurous acid, H₂SO₃

Peroxodisulphuric acid, H₂S₂O₇

Sulphuric acid, H₂SO₄

O.S = +4

Dibasic

Peroxy

linkage

O.S = +6

Dibasic

Pyrosulphuric acid, H₂S₂O₇

Oxy

linkage

232 of 454

Sulphuric acid

Sulphuric acid (H₂SO₄)

Preparation of H₂SO₄

Air

Sulphur

Dust

precpitator

Step 1- SO₂ + O₂

Impure

Water spray

Conc. H₂SO₄

Washing &

Cooling tower

Waste

water

Waste

acid

Drying

tower

Dry SO₂ + O₂

Preheater

As purifier containing

gelatinous hydrated ferric oxide

V₂O₅

SO₃

Conc. H₂SO₄

Oleum H₂S₂O₇

Catalytic

converter

Quartz

Step 2

Step 3

Plant is operated at 2 atm & 720 K

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Sulphuric acid (H₂SO₄)

Preparation of H₂SO₄

Key Step – 2SO₂(g) + O₂(g) 2SO₃(g)

V₂O₅

Reaction is exothermic, reversible & forward reaction leads to decrease in volume

According to LeChatelier’s principle

Low temperature leads to forward reaction

High pressure leads to forward reaction

Should not be too low or reaction would become slow

Oleum H₂S₂O₇

Dilution with water

Sulphuric acid H₂SO₄

Formation of oleum – SO₃ + H₂SO₄ H₂S₂O₇

H₂SO₄ obtained by contact process is 96 -98% pure

Sulphuric acid

234 of 454

Sulphuric acid (H₂SO₄)

Properties of H₂SO₄

Physical properties

Colorless, dense, oily liquid

Water

Acid

Highly exothermic

Sulphuric acid

Specific gravity = 1.84 at 298 K

Freezing point – 283 K

Boiling point – 611 K

235 of 454

Sulphuric acid (H₂SO₄)

Properties of H₂SO₄

Chemical properties

Strong acidic character in water

Sulphuric acid

236 of 454

Sulphuric acid

Sulphuric acid (H₂SO₄)

Properties of H₂SO₄

Chemical properties

Volatile nature allows manufacturing of more volatile acid

H₂SO₄+ MX 2HX + M₂SO₄ (aq)

M – metal , X – F, Cl, NO₃

Types of sulphates

Normal sulphate

Acidic sulphate

Na₂SO₄

CuSO₄

NaHSO₄

237 of 454

Sulphuric acid

Sulphuric acid (H₂SO₄)

Properties of H₂SO₄

Chemical properties

Dehydrating agent

2H₂SO₄ (conc) + Cu CuSO₄ + 2H₂O + SO₂

Moderately strong oxidizing agent

H₂SO₄+ C₁₂H₂₂O₁₁ 12C + 11H₂O

Act as dehydrating agent for many gases but it should not react with gases

2H₂SO₄ (conc) + S 2H₂O + 3SO₂

2H₂SO₄ (conc) + C 2H₂O + 2SO₂ + CO₂

Intermediate between

H₃PO₄ and HNO₃

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Sulphuric acid

Sulphuric acid (H₂SO₄)

Refining petroleum

Uses of H₂SO₄

Manufacturing of nitrocellulose products

Manufacturing of fertilisers

(NH₄)₂SO₄

Detergent industry and storage batteries

Metallurgical applications

Manufacturing of pigments, paints and dyestuff intermediates

Cleansing metals before enameling, electroplating

Also used as laboratory reagent

239 of 454

Q. Why is K_a1 is not equal to K_a2 for H₂SO₄ in water?

Pause the video

Time duration - 2 min

NCERT, Exercise question – 7.25

Page no. 197

240 of 454

Q. Why is K_a1 is not equal to K_a2 for H₂SO₄ in water?

Sol.

Neutral molecule

Charged molecule

Removal of H⁺ is difficult from charged molecule than from neutral molecule

Thus K_a1 is larger than K_a2

241 of 454

PSV 03

12C07.4

242 of 454

Q. What are the conditions to maximize the yield of H₂SO₄ by contact process?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.24

Page no. 197

243 of 454

Q. What are the conditions to maximize the yield of H₂SO₄ by contact process?

Key step in the manufacture of H₂SO₄ –

2SO₂(g) + O₂(g) 2SO₃

V₂O₅

This is exothermic reaction Δ_rH^o = -198.6 kJ/mol

According to Lechatelier’s principle

For exothermic reaction , Temperature

Forward Reaction

But temperature should not be too low otherwise reaction will not start

Optimum Conditions are Pressure – 2 bar

Temperature – 720 K

SO₃

Final step in the manufacture of H₂SO₄ –

H₂SO₄

H₂S₂O₇

Sol.

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Summary

Preparation of O₂ -

2KClO₃ 2KCl + 3O₂

P₄ + 5O₂ P₄O₁₀

2ZnS + 3O₂ 2ZnO + 2SO₂

2SO₂ + O₂ 2SO₃

4HCl + O₂ 2Cl₂ + 2H₂O

V₂O₅

CuCl₂

Properties of O₂

Properties of SO₂

SO₂(g) + H₂O(l) H₂SO₃

SO₂ + 2NaOH Na₂SO₃ + H₂O

Na₂SO₃ + H₂O + SO₂ 2NaHSO₃

5SO₂ + 2MnO₄^- + 2H₂O 2Mn²⁺ + 5SO₄^2- + 4 H⁺

Properties of O₃

PbS(s) + 4O₃(g) PbSO₄(s) + 4O₂(g)

2I ^- (aq) + H₂O(l) + O₃(g) 2OH^- (aq) + O₂(g) + I₂(s)

NO(g) + O₃(g) O₂(g) + NO₂(g)

2H₂SO₄ (conc) + Cu CuSO₄ + 2H₂O + SO₂

H₂SO₄+ C₁₂H₂₂O₁₁ 12 C + 11 H₂O

2H₂SO₄ (conc) + S 2H₂O + 3SO₂

2H₂SO₄ (conc) + C 2H₂O + 2SO₂ + CO₂

Properties of H₂SO₄

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Reference Questions

Intext Question, NCERT : 7.18, Page no. – 192

7.20, Page no. – 194

7.21, Page no. – 194

7.23, Page no. – 197

Example Question, NCERT : 7.12, Page no. – 193

7.13, Page no. – 197

Exercise Question, NCERT : 7.20, Page no. – 213

7.21, Page no. – 213

Workbook Questions: 7, 8

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Q. Why do noble gases have comparatively large atomic sizes?

Pause the video

Time duration - 2 min

NCERT, Exercise question – 7.39

Page no. 214

248 of 454

Q. Why do noble gases have comparatively large atomic sizes?

Sol.

Covalent radii

Vanderwall radii

Covalent radii

Vanderwall radii

Noble gases have vanderwall forces between them all the other elements of p block are calculates using covalent radii

Thus noble gases have large atomic sizes

249 of 454

Q. Why helium is used in diving apparatus?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.32

Page no. 211

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Q. Why helium is used in diving apparatus?

Sol.

CO₂

Others

Composition of air

Very large amount

On going down solubility of N₂ gas in blood increases as P also increases

After coming at surface solubility of N₂ decreases and it separates from blood

Thus creating bubbles leading

to disease BENDS

Thus He is used in O₂ cylinders

Because of its low solubility in blood

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Q. Does the hydrolysis of XeF₆ lead to redox reaction?

Pause the video

Time duration - 2 min

NCERT, Example question – 7.22

Page no. 211

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Q. Does the hydrolysis of XeF₆ lead to redox reaction?

Sol.

No change in Oxidation state of

1.) Xe

2.) F

3.) O

No change in Oxidation state

1.) Xe

2.) F

3.) O

Thus Hydrolysis of XeF₆ does not lead to oxidation of any of the species

253 of 454

Q. Give the reason for bleaching action of Cl₂. Name the two poisonous gases which can be prepared from Cl₂

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.29, 7.30

Page no. 204

254 of 454

Q. Give the reason for bleaching action of Cl₂. Name the two poisonous gases which can be prepared from Cl₂

Sol.

The reason for bleaching action of Cl₂ is due to oxidation.

Bleaching action of Cl₂ is only in presence of moisture

Nascent Oxygen

Colored Substance + O

Colorless Substance

Two poisonous gases

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Q. When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Why?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.18

Page no. 205

256 of 454

Q. When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Why?

Sol.

Reaction of HCl with Iron

Oxidation of Fe from +2 to +3

Act as reducing agent

Thus it prevent formation of ferric chloride

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Pause the video

Time duration - 2 min

NCERT, Intext question – 7.18

Page no. 205

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p orbital of chlorine

p orbital of iodine

Different size of p

orbital

Same size of p

orbital

Overlapping extent

Is better thus stronger

bonding

Sol.

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12C07.5��Group 17 Elements – The Halogen Family

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12C07.5 Group 17 Elements – The Halogen Family

Learning Objectives

Introduction and occurrence of halogen family

Atomic and physical properties of halogens

Chemical properties of halogens

Chlorine

Hydrogen chloride

Oxoacids of halogens

Interhalogen compounds

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12C07.5

CV 1

Introduction and occurrence of Halogen family

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Introduction and occurrence of Halogen family

Introduction to Halogens

Halo genes

Salt

Borne

Salt producers

Fluorine

Chlorine

Bromine

Iodine

Astatine

Tennessine

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Introduction and occurrence of Halogen family

Soil

Animal teeth and bones

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Introduction and occurrence of Halogen family

Cl, Br and I

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12C07.5

CV 2

Atomic and Physical Properties of Halogens

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Atomic and Physical Properties of Halogens

Element	Atomic Number	Atomic mass (g mol^–1)	Electronic Configuration

Fluorine, F	9	19	[He] 2s²2p⁵

Chlorine, Cl	17	35.45	[Ne] 3s² 3p⁵

Bromine, Br	35	79.90	[Ar] 3d¹⁰ 4s² 4p⁵

Iodine, I	53	126.90	[Kr] 4d¹⁰ 5s² 5p⁵

Astetine, As	85	210	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵

Tennessine, Ts	117	294	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵

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Atomic and Physical Properties of Halogens

Electronic Configuration

Element	Atomic Number	Electronic Configuration

Fluorine, F	9	[He] 2s²2p⁵

Chlorine, Cl	17	[Ne] 3s² 3p⁵

Bromine, Br	35	[Ar] 3d¹⁰ 4s² 4p⁵

Iodine, I	53	[Kr] 4d¹⁰ 5s² 5p⁵

General Electronic Configuration

ns²np⁵

Filled Inner d - orbitals

7 Electrons in outer most shell

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Atomic and Physical Properties of Halogens

Atomic and Ionic Radii

Element	Atomic Number	Covalent Radii pm	Ionic Radii pm

Fluorine, F	9	64	133

Chlorine, Cl	17	99	184

Bromine, Br	35	114	196

Iodine, I	53	133	220

Covalent and Ionic Radii increase

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Atomic and Physical Properties of Halogens

Atomic Radii vs Ionic Radii

Proton = 9

Electrons = 9

Proton = 9

Electrons = 10

₉F, Covalent radius = 64 pm

₉F, Ionic radius = 133 pm

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Atomic and Physical Properties of Halogens

Atomic Radii vs Ionic Radii

Chlorine

Bromine

Iodine

Chloride ion

Bromide ion

Iodide ion

Covalent Radii

Ionic Radii

99 pm

184 pm

114 pm

196 pm

133 pm

220 pm

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Atomic and Physical Properties of Halogens

Element	Atomic Number	Covalent Radii pm	Ionization Enthalpy

Fluorine, F	9	64	1680 kJ mol^–1

Chlorine, Cl	17	99	1256 kJ mol^–1

Bromine, Br	35	114	1142 kJ mol^–1

Iodine, I	53	133	1008 kJ mol^–1

Covalent radii increase

Ionization enthalpy decrease

Ionization Enthalpy

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Atomic and Physical Properties of Halogens

Ionization Enthalpy

Distance between nucleus and outer most electron increases

Ionization enthalpy decreases

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Atomic and Physical Properties of Halogens

Element	Atomic Number	Covalent Radii pm	Electron Gain Enthalpy (kj mol^-1)

Fluorine, F	9	64	- 333

Chlorine, Cl	17	99	- 349

Bromine, Br	35	114	- 325

Iodine, I	53	133	- 296

Covalent radii increase

Less negative electron gain enthalpy

Electron Gain Enthalpy

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Atomic and Physical Properties of Halogens

Element	Atomic Number	Covalent Radii pm	Electron Gain Enthalpy (kj mol^-1)

Fluorine, F	9	64	- 333

Chlorine, Cl	17	99	- 349

Bromine, Br	35	114	- 325

Iodine, I	53	133	- 296

Exception

Electron Gain Enthalpy

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Atomic and Physical Properties of Halogens

Distance between nucleus and outer most shell increases

Electron gain enthalpy becomes less negative

Electron Gain Enthalpy

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Atomic and Physical Properties of Halogens

Element	Atomic Number	Covalent Radii pm	Electronegativity

Fluorine, F	9	64	4

Chlorine, Cl	17	99	3.2

Bromine, Br	35	114	3

Iodine, I	53	133	2.7

Covalent radii increase

Electronegativity decrease

Electronegativity

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Melting point, Boiling point and Density

Atomic Number

M.P (K)

54.4

172

265.8

386.6

B.P (K)

84.9

239

332.5

458.2

Density (g cm^-3)

1.5

1.66

3.19

4.94

Bond dissociation enthalpy (kj mol^-1)

158.8

242.6

192.8

151.1

Atomic and Physical Properties of Halogens

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12C07.5

PSV 1

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Q. Why is the electron gain enthalpy of chlorine is more negative than that of fluorine?

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Time duration - 2 min

Q. Why is the electron gain enthalpy of chlorine is more negative than that of fluorine?

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Sol.

Q. Why is the electron gain enthalpy of chlorine is more negative than that of fluorine?

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High repulsion with outer most electrons

Less repulsion with outer most electrons

- 333 kj mol^-1

- 349 kj mol^-1

Sol.

Q. Why is the electron gain enthalpy of chlorine is more negative than that of fluorine?

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12C07.5

PSV 2

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Q. Halogens have maximum negative electron gain enthalpy in the respective periods of the periodic table. Why?

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Pause the video

Time duration - 2 min

Q. Halogens have maximum negative electron gain enthalpy in the respective periods of the periodic table. Why?

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Sol.

Q. Halogens have maximum negative electron gain enthalpy in the respective periods of the periodic table. Why?

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152 pm

111 pm

88 pm

77 pm

74 pm

66 pm

64 pm

High effective nuclear charge

Readily accept one electron to acquire noble gas electronic configuration

Sol.

Q. Halogens have maximum negative electron gain enthalpy in the respective periods of the periodic table. Why?

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ConcepTest

Ready for Challenge

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Q. Why does the bond dissociation enthalpy of F₂ molecule is lesser than that of Cl₂ molecule?

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Pause the video

Time duration - 2 min

Q. Why does the bond dissociation enthalpy of F₂ molecule is lesser than that of Cl₂ molecule?

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Sol.

Q. Why does the bond dissociation enthalpy of F₂ molecule is lesser than that of Cl₂ molecule?

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Ideally

B.D.E of F₂ > B.D.E of Cl₂

Reality

B.D.E of F₂ < B.D.E of Cl₂

Cause: High electron-electron repulsion among the lone pairs in small size F₂ molecule

158.8 (kj mol^-1)

242.6 (kj mol^-1)

Sol.

Q. Why does the bond dissociation enthalpy of F₂ molecule is lesser than that of Cl₂ molecule?

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12C07.1

CV 3

Chemical Properties

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Chemical Properties of Halogens

Chemical Properties

Oxidation states

Halogen atom�in ground state�(other than fluorine)

1st excited state

2nd excited state

3rd excited state

Ground state of F

1 unpaired e accounts for –1 or +1 oxidation state

3 unpaired e account

for +3 oxidation states

5 unpaired e account

for +5 oxidation state

7 unpaired e account for +7 oxidation state

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Chemical Properties of Halogens

Oxidation states

Higher oxidation states of F

d – orbital

Only -1 O.S

Higher oxidation states of Cl, Br and I

Cl, Br and I

F or O

Interhalogen and oxoacids

+4 and +5 O.S of Cl and Br

Oxides and oxoacids

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Chemical Properties of Halogens

Elements

Chemical Reactivity decreases down the group

Chemical Reactivity

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Chemical Properties of Halogens

Oxidising nature

Small sized halogen

Noble gas electronic configurations

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Chemical Properties of Halogens

Elements

X = Cl, Br and I

X = Br and I

X = I

Oxidising nature

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Chemical Properties of Halogens

Reaction with water

-2

Oxidation

X = Cl or Br

-1

Oxidation

Reduction

-1

Oxidation

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Chemical Properties of Halogens

Anomalous behavior of fluorine

Ionization enthalpy

Electronegativity

Electrode potentials

Higher than expected

Ionic and covalent radii

m.p. and b.p.

Bond dissociation enthalpy

Electron gain enthalpy

Quite lower than expected

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Chemical Properties of Halogens

F undergoes exothermic reactions

HF is liquid due to H-bonding

H-bond

Anomalous behavior of fluorine

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Chemical Properties of Halogens

Reason for anomalous behavior of fluorine

64 pm

Small size

High electronegativity

d – orbital

Small B.D.E

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Chemical Properties of Halogens

Chemical Properties

Reactivity towards

Other halogens

Hydrogen

Oxygen

Metals

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Chemical Properties of Halogens

Chemical Properties

Reactivity towards hydrogen

Reactants

Intermediate

Product

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Chemical Properties of Halogens

Reactivity towards hydrogen

Chemical Properties

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Chemical Properties of Halogens

Chemical Properties

Small bond length

Difficult to break

High B.D.E

weaker acid

Large bond length

Easy to break

Low B.D.E

stronger acid

Reactivity towards hydrogen

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Chemical Properties of Halogens

	160.9	295	- 10	222	238

	141.4	363	- 9.5	185	206

	127.4	432	- 7	159	189

	91.7	574	3.2	190	293

	Bond Length (pm)	B.D.E (kj mol^-1)		M.P (K)	B.P (K)

Properties of HX

Chemical Properties

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Chemical Properties of Halogens

Chemical Properties

Oxygen difluoride

Oxygen fluoride

Thermally stable

Strong fluorinating agents

Unstable

Reactivity towards oxygen

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Chemical Properties of Halogens

Stability order

Reactivity towards oxygen

Greater polarisability of bond between

iodine and oxygen

Multiple bond formation

between Cl and O due to availability of d–orbitals

Both the factors are unavailable

Chemical Properties

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Chemical Properties of Halogens

Reactivity towards metals

MCl

MBr

Ionic character

Chemical Properties

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Chemical Properties of Halogens

Reactivity towards metals

Higher O.S metal halides

Lower O.S metal halides

More covalent

Chemical Properties

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Chemical Properties of Halogens

Reactivity towards halogens

Chemical Properties

Xʹ

Interhalogen compounds

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12C07.1

CV 4

Chlorine

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Chlorine

Discovered by Scheele in 1774

Named as chlorine by Humphry Davy

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Chlorine

Other methods

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Chlorine

Deacon’s process

HCl + Air

Catalytic chamber

Cooler

Quartz

Washing tower

Drying tower

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Chlorine

Electrolytic process

Electrolysis of molten NaCl

Cathode

Anode

Na at Cathode

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Chlorine

Properties of chlorine

Physical properties

Chemical properties

Greenish yellow gas
Pungent and suffocating odour
2-5 times heavier than air
Liquefied easily
Soluble in water

Reaction with metals and non metals
Reaction with hydrogen
Reaction with bases
Reaction with hydrocarbons
Oxidising nature
Bleaching nature

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Chlorine

Reaction with metals and non metals

Chemical properties

2Fe + 3Cl₂ → 2FeCl₃

Reaction with metals

Reaction with non metals

Reaction with hydrogen and its compounds

P₄ + 6Cl₂ → 4PCl₃

H₂S + Cl₂ → 2HCl + S

S₈ + 4Cl₂ → 4S₂Cl₂

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Chlorine

Reaction with Bases

Chemical properties

With cold and dilute alkalies

Reaction with hot and concentrated alkalies

6NaOH + 3Cl₂ → 5NaCl + NaClO₃ + 3H₂O

Sodium hypochlorite

Sodium chlorate

Cold and dilute

Hot and concentrated

Reaction with calcium hydroxide

Bleaching powder

Composition of bleaching powder

Ca(OCl)₂.CaCl₂.Ca(OH)₂.2H₂O

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Chlorine

Reaction with Hydrocarbons

Chemical properties

Methane

Chloromethane

Substitution products with saturated hydrocarbons

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Chlorine

Reaction with Hydrocarbons

Chemical properties

Ethene

Chloroethane

Addition products with unsaturated hydrocarbons

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Chlorine

Oxidising Nature

Chemical properties

Light

Colour will fade

HCl + HOCl

2HOCl 2HCl + 2[O]

Nascent oxygen

High energy

Small life time

High oxidising power

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Chlorine

Oxidising Nature

Chemical properties

Oxidation

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Chlorine

Bleaching Nature

Chemical properties

Coloured substance + [O] → Colourless substance

Cl₂ + H₂O → 2HCl + [O]

[ O ]

Coloured substance

Colourless substance

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Chlorine

Bleaching

Uses of Chlorine

Elephant teeth

Flower petals

Wood pulp

Cotton

Fruits and vegetables

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Chlorine

Uses of Chlorine

Extraction

Manufacture

Drugs

Dyes

DDT

Chloroform

Gold

Platinum

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Chlorine

Uses of Chlorine

Preparation of poisonous gases

Mustard gas (ClCH₂CH₂SCH₂CH₂Cl)

Tear gas

(CCl₃NO₂)

Phosgene (COCl₂)

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12C07.1

CV 4

Hydrogen Chloride

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Hydrogen Chloride

Hydrogen chloride, HCl

Prepared by Glauber in 1648

Humphry Davy told it is a compound of H and Cl

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Hydrogen Chloride

NaCl + H₂SO₄ NaHSO₄ + HCl

420 K

NaHSO₄ + NaCl Na₂SO₄ + HCl

420 K

Gas jar

HCl Gas

Preparation of HCl

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Hydrogen Chloride

Properties of hydrogen chloride

Physical properties

Chemical properties

Colourless gas
Pungent smelling
Colourless in liquid state
White in crystalline state
Extremely soluble in water

Ionizes in water
Reaction with ammonia
Formation of aqua regia
Reaction with salts of weaker acids

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Hydrogen Chloride

Chemical Properties of hydrogen chloride

HCl gas

Ionization in water

H₃O⁺ ion

H₂O

K_a =10⁷

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Hydrogen Chloride

Chemical Properties of hydrogen chloride

Reaction with ammonia

NH₃

HCl

White and dense fumes of NH₄Cl

Base

Acid

Salt

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Hydrogen Chloride

Chemical Properties of hydrogen chloride

Formation of aqua regia

1 vol. conc. HNO₃

3 vol. conc. HCl

Aqua regia

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Hydrogen Chloride

Chemical Properties of hydrogen chloride

Reaction with salts of weaker acids

Salt of carbonic acid

Salt of sulphuric acid

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Hydrogen Chloride

Uses of hydrogen chloride

Manufacture

NH₄Cl

C₆H₁₂O₆

Purification

Bone black

laboratory reagent

Medicines

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12C07.5

PSV 3

339 of 454

12C07.5 Group 17 Elements – The Halogen Family

Q. When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Why?

Sol.

FeCl₃

Reducing agent

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12C07.5

PSV 4

341 of 454

Q. When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Why?

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.18

Page no. 205

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FeCl₃

Reducing agent

Q. When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Why?

Sol.

343 of 454

Q. When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Why?

Sol.

Reaction of HCl with Iron

Oxidation of Fe from +2 to +3

Act as reducing agent

Thus it prevent formation of ferric chloride

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12C07.6

CV 5

Oxoacids of Halogens

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12C07.5 Group 17 Elements – The Halogen Family

Oxoacids of Halogens

Contain oxygen, hydrogen and other non metallic element

Halic (I) acid �(Hypohalous acid)
Halic (III) acid �(Halous acid)
Halic (V) acid �(Halic acid)
Halic (VII) acid �(Perhalic acid)


– �–
– �–
– �–


– �–


–�–

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12C07.5 Group 17 Elements – The Halogen Family

Oxoacids of Halogens

Nomenclature

-ous

Chlorous acid

-ic

Chloric acid

Hypo - ous

Hypochlorous acid

Per - ic

perchloric acid

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12C07.5 Group 17 Elements – The Halogen Family

Oxoacids of Chlorine

Chlorous acid

Chloric acid

Hypochlorous acid

Perchloric acid

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12C07.1

CV 4

Interhalogen Compounds

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12C07.5 Group 17 Elements – The Halogen Family

Xʹ

Interhalogen compounds

Xʹ

Larger in size

Smaller in size

More electropositive

Less electropositive

XXʹ

XXʹ₃

XXʹ₅

XXʹ₇

Bent ‘T’ shape

Square pyramidal

Pentagonal bipyramidal

Linear

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12C07.5 Group 17 Elements – The Halogen Family

Preparation of Interhalogen compounds

Equal volume

Excess

Diluted

Equimolar

Excess

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Type	Formula	Physical state and column	Structure
		Colourless gas
		Pale brown gas
		Detected spectroscopically
		Gas

		Black solid
		Colourless gas	Bent T – shaped
		Yellow green liquid	Bent T – shaped
		Yellow powder	Bent T – shaped (?)
		Orange solid	Bent T – shaped (?)
			Square Pyramidal
		Colourless liquid	Square
		Colourless liquid	Pyramidal
		Colourless gas	Pentagonal

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12C07.5 Group 17 Elements – The Halogen Family

Physical properties of Interhalogen compounds

Covalent molecules

Diamagnetic in nature

Volatile solids or liquids at 298 K except ClF(g)

Physical properties are intermediate between those of constituent halogens

m.p. and b.p. are a little higher than expected

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12C07.5 Group 17 Elements – The Halogen Family

Chemical properties of Interhalogen compounds

Fluorine

Xʹ

Chemical reactivity

Interhalogen

Other halogen

Weak bond

Strong bond

Inter electronic repulsion

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12C07.5 Group 17 Elements – The Halogen Family

Chemical properties of Interhalogen compounds

Hydrolysis

XXʹ

XXʹ₃

XXʹ₅

XXʹ₇

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12C07.5 Group 17 Elements – The Halogen Family

Sol.

VSEPR theory

bp-bp < lp-bp > lp-lp

No repulsion

bp-bp

bp-lp

lp-lp = 0

lp-bp = 4

bp-bp = 2

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Pause the video

Time duration - 2 min

NCERT, Intext question – 7.18

Page no. 205

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p orbital of chlorine

p orbital of iodine

Different size of p

orbital

Same size of p

orbital

Overlapping extent

Is better thus stronger

bonding

Sol.

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12C07.5 Group 17 Elements – The Halogen Family

Uses of Interhalogen compounds

Used as non aqueous solvents

Very useful fluorinating agents

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Q. Give the reason for bleaching action of Cl₂. Name the two poisonous gases which can be prepared from Cl₂

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.29, 7.30

Page no. 204

361 of 454

Q. Give the reason for bleaching action of Cl₂. Name the two poisonous gases which can be prepared from Cl₂

Sol.

The reason for bleaching action of Cl₂ is due to oxidation.

Bleaching action of Cl₂ is only in presence of moisture

Nascent Oxygen

Colored Substance + O

Colorless Substance

Two poisonous gases

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12C07.6��Group 18 Elements – The Noble gases

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12C07.6 Group 18 Elements – The Noble gases

Learning Objectives

Introduction and occurrence of Noble gases

Atomic and physical properties of Noble gases

Physical and Chemical properties of Noble gases

Uses of Noble gases

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12C07.6

CV 1

Introduction and occurrence of Noble gases

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Introduction and occurrence of Noble gases

Introduction to Noble gases

Helium

Neon

Argon

Krypton

Radon

Oganesson

Xenon

Chemically unreactive

Form very few compounds

Group 18 elements

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Introduction and occurrence of Noble gases

Major constituent

Occurrence of Noble gases

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Rarest element

Synthetic element

Introduction and occurrence of Noble gases

Occurrence of Noble gases

Pitchblende

Monazite

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12C07.6

CV 2

Atomic and Physical Properties of Noble gases

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Atomic and Physical Properties of Noble gases

Element	Atomic Number	Atomic mass (g mol^–1)	Electronic Configuration

He	2	4	1s²

Ne	10	20.18	[He] 2s² 2p⁶

Ar	18	39.95	[Ne] 3s² 3p⁶

Kr	36	83.80	[Ar] 3d¹⁰4s² 4p⁶

Xe	54	131.30	[Kr] 4d¹⁰5s² 5p⁶

Rn	86	222	[Xe] 4f¹⁴5d¹⁰6s² 6p⁶

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Atomic and Physical Properties of Noble gases

Element	Atomic Number	Electronic Configuration

He	2	1s²

Ne	10	[He] 2s² 2p⁶

Ar	18	[Ne] 3s² 3p⁶

Kr	36	[Ar] 4s² 4p⁶

Xe	54	[Kr] 5s² 5p⁶

Rn	86	[Xe] 6s² 6p⁶

Electronic Configuration

General Electronic Configuration

ns²np⁶

8 Electrons in outer most shell

Exception He – No p-orbital

Inert nature

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Atomic Radius

Element	Atomic Number	Atomic Radius pm

He	2	120

Ne	10	160

Covalent Radii increase

Ar	18	190

Kr	36	200

Xe	54	220

Rn	86	_

Atomic and Physical Properties of Noble gases

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Atomic and Physical Properties of Noble gases

Element	Atomic Number	Atomic Radius pm	Ionization enthalpy

He	2	120	2372

Ne	10	160	2080

Ar	18	190	1520

Kr	36	200	1351

Xe	54	220	1170

Rn	86	_	1037

Covalent radii increase

Ionization enthalpy decrease

Ionization Enthalpy

Electronic configuration

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Ionization Enthalpy

Distance between nucleus and outer most electron increases

Ionization enthalpy decreases

Atomic and Physical Properties of Noble gases

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Atomic and Physical Properties of Noble gases

Element	Atomic Number	Atomic Radius pm	E.G.E

He	2	120	48

Ne	10	160	116

Ar	18	190	96

Kr	36	200	96

Xe	54	220	77

Rn	86	_	68

Electron gain enthalpy

Stable Electronic configuration

No tendency to accept electron

Large positive E.G.E

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Melting point, Boiling point and Density

Atomic Number

M.P (K)

24.6

83.8

115.9

B.P (K)

4.2

27.1

87.2

119.7

Density

(g cm^-3)

1.8×10^–4

9.0×10^–4

1.8×10^–3

3.7×10^–3

Atomic and Physical Properties of Halogens

161.3

165

5.9×10^–3

202

211

9.7×10^–3

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12C07.6

CV 3

Physical and Chemical Properties of Noble gases

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Physical and Chemical Properties of Noble gases

Physical Properties

Monoatomic

Colourless, odourless and tasteless

Sparingly soluble in water

Very low melting and boiling points

Helium has the lowest b.p (4.2 K) of any known substance

He can diffuse through most commonly used laboratory materials such as

rubber, glass or plastics.

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Physical and Chemical Properties of Noble gases

Chemical Properties

Neil Bartlett

Prepared first compound of Xe

Red coloured

With fluorine

With oxygen

He, Ne and Ar

No true compounds

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Physical and Chemical Properties of Noble gases

Compounds of Xe

Xenon – Fluorine compounds

Xenon – Oxygen compounds

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Physical and Chemical Properties of Noble gases

Xenon – Fluorine compounds

Colourless crystalline solid

Sublime at 298 K

Powerful fluorinating agent

Hydrolysed by traces of water

Linear with 3 l.p

Excess

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Physical and Chemical Properties of Noble gases

Xenon – Fluorine compounds

Colourless crystalline solid

Sublime at 298 K

Powerful fluorinating agent

Hydrolysed by traces of water

Square planar with 2 l.p

1 : 5 Ratio

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Physical and Chemical Properties of Noble gases

Xenon – Fluorine compounds

Colourless crystalline solid

Sublime at 298 K

Powerful fluorinating agent

Hydrolysed by traces of water

Distorted octahedral with 2 l.p

1 : 20 Ratio

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Physical and Chemical Properties of Noble gases

Xenon – Oxygen compounds

Square pyramidal with 1 l.p

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Physical and Chemical Properties of Noble gases

Xenon – Oxygen compounds

See-saw with 1 l.p

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Physical and Chemical Properties of Noble gases

Xenon – Oxygen compounds

Pyramidal with 1 l.p

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12C07.6

CV 4

Uses of Noble gases

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Uses of Noble gases

Meteorological observations

Gas-cooled nuclear reactors

Liq. He – B.P 4.2 K

cryogenic agent

Powerful superconducting magnets for MRI machines

Modern diving apparatus

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Uses of Noble gases

Discharge tube

Fluorescent bulbs

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Uses of Noble gases

Arc welding

Electric bulbs

Provide inert atmosphere

Uses of Noble gases

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Q. Why do noble gases have comparatively large atomic sizes?

Pause the video

Time duration - 2 min

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Q. Why do noble gases have comparatively large atomic sizes?

Sol.

Covalent radii

Van der Wall radii

Covalent radii

Van der Wall radii

Noble gases have Van der Wall forces between them all the other elements of p block are calculates using covalent radii

Thus noble gases have large atomic sizes

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Q. Why helium is used in diving apparatus?

Pause the video

Time duration - 2 min

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Q. Why helium is used in diving apparatus?

Sol.

CO₂

Others

Composition of air

Very large amount

On going down solubility of N₂ gas in blood increases as P also increases

After coming at surface solubility of N₂ decreases and it separates from blood

Thus creating bubbles leading

to disease BENDS

Thus He is used in O₂ cylinders

Because of its low solubility in blood

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Summery

Group 18 elements are called noble gases because of their inert nature

They show large positive electron gain enthalpy

Compounds of Xe are XeF₂, XeF₄, XeF₆, XeOF₄, XeO₂F₂, XeO₃

General electronic configuration is ns² np⁶, for He it is 1s²

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Reference Questions

Intext Question, NCERT : 7.32, Page no. – 205

7.33, Page no. – 205

7.34, Page no. – 205

Example Question, NCERT : 7.22, Page no. – 205

Exercise Question, NCERT : 7.33, Page no. – 208

7.35, Page no. – 208

7.37, page no. – 208

7.39, page no. – 208

7.40, page no. – 208

Workbook Questions: 7, 8

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Q. Does the hydrolysis of XeF₆ lead to redox reaction?

Pause the video

Time duration - 2 min

NCERT, Example question – 7.22

Page no. 211

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Q. Does the hydrolysis of XeF₆ lead to redox reaction?

Sol.

No change in Oxidation state of

1.) Xe

2.) F

3.) O

No change in Oxidation state

1.) Xe

2.) F

3.) O

Thus Hydrolysis of XeF₆ does not lead to oxidation of any of the species

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Q. Give the reason for bleaching action of Cl₂. Name the two poisonous gases which can be prepared from Cl₂

Pause the video

Time duration - 2 min

NCERT, Intext question – 7.29, 7.30

Page no. 204

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Chemical Properties of Noble gases

Xenon – Fluorine compounds

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Chemical Properties of Noble gases

Xenon – Fluorine compounds

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Chemical Properties of Noble gases

Xenon – Fluorine compounds

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Chemical Properties of Halogens

F undergoes exothermic reactions

HF is liquid due to H-bonding

H-bond

Anomalous behavior of fluorine

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Chemical Properties of Halogens

Reason for anomalous behavior of fluorine

64 pm

Small size

High electronegativity

d – orbital

Small B.D.E

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Chemical Properties of Halogens

Chemical Properties

Reactivity towards

Other halogens

Hydrogen

Oxygen

Metals

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Chemical Properties of Halogens

Chemical Properties

Reactivity towards hydrogen

Reactants

Intermediate

Product

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Chemical Properties of Halogens

Reactivity towards hydrogen

Chemical Properties

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Chemical Properties of Halogens

Chemical Properties

Small bond length

Difficult to break

High B.D.E

weaker acid

Large bond length

Easy to break

Low B.D.E

stronger acid

Reactivity towards hydrogen

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Chemical Properties of Halogens

	160.9	295	- 10	222	238

	141.4	363	- 9.5	185	206

	127.4	432	- 7	159	189

	91.7	574	3.2	190	293

	Bond Length (pm)	B.D.E (kj mol^-1)		M.P (K)	B.P (K)

Properties of HX

Chemical Properties

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Chemical Properties of Halogens

Chemical Properties

Oxygen difluoride

Oxygen fluoride

Thermally stable

Strong fluorinating agents

Unstable

Reactivity towards oxygen

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Chemical Properties of Halogens

Stability order

Reactivity towards oxygen

Greater polarisability of bond between

iodine and oxygen

Multiple bond formation

between Cl and O due to availability of d–orbitals

Both the factors are unavailable

Chemical Properties

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Chemical Properties of Halogens

Reactivity towards metals

MCl

MBr

Ionic character

Chemical Properties

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Chemical Properties of Halogens

Reactivity towards metals

Higher O.S metal halides

Lower O.S metal halides

More covalent

Chemical Properties

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Chemical Properties of Halogens

Reactivity towards halogens

Chemical Properties

Xʹ

Interhalogen compounds

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12C07.1

CV 4

Chlorine

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Chlorine

Discovered by Scheele in 1774

Named as chlorine by Humphry Davy

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Chlorine

Other methods

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Chlorine

Deacon’s process

HCl + Air

Catalytic chamber

Cooler

Quartz

Washing tower

Drying tower

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Chlorine

Electrolytic process

Electrolysis of molten NaCl

Cathode

Anode

Na at Cathode

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Chlorine

Properties of chlorine

Physical properties

Chemical properties

Greenish yellow gas
Pungent and suffocating odour
2-5 times heavier than air
Liquefied easily
Soluble in water

Reaction with metals and non metals
Reaction with hydrogen
Reaction with bases
Reaction with hydrocarbons
Oxidising nature
Bleaching nature

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Chlorine

Reaction with metals and non metals

Chemical properties

2Fe + 3Cl₂ → 2FeCl₃

Reaction with metals

Reaction with non metals

Reaction with hydrogen and its compounds

P₄ + 6Cl₂ → 4PCl₃

H₂S + Cl₂ → 2HCl + S

S₈ + 4Cl₂ → 4S₂Cl₂

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Chlorine

Reaction with Bases

Chemical properties

With cold and dilute alkalies

Reaction with hot and concentrated alkalies

6NaOH + 3Cl₂ → 5NaCl + NaClO₃ + 3H₂O

Sodium hypochlorite

Sodium chlorate

Cold and dilute

Hot and concentrated

Reaction with calcium hydroxide

Bleaching powder

Composition of bleaching powder

Ca(OCl)₂.CaCl₂.Ca(OH)₂.2H₂O

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Chlorine

Reaction with Hydrocarbons

Chemical properties

Methane

Chloromethane

Substitution products with saturated hydrocarbons

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Chlorine

Reaction with Hydrocarbons

Chemical properties

Ethene

Chloroethane

Addition products with unsaturated hydrocarbons

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Chlorine

Oxidising Nature

Chemical properties

Light

Colour will fade

HCl + HOCl

2HOCl 2HCl + 2[O]

Nascent oxygen

High energy

Small life time

High oxidising power

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Chlorine

Oxidising Nature

Chemical properties

Oxidation

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Chlorine

Bleaching Nature

Chemical properties

Coloured substance + [O] → Colourless substance

Cl₂ + H₂O → 2HCl + [O]

[ O ]

Coloured substance

Colourless substance

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Chlorine

Bleaching

Uses of Chlorine

Elephant teeth

Flower petals

Wood pulp

Cotton

Fruits and vegetables

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Chlorine

Uses of chlorine

Extraction

Manufacture

Drugs

Dyes

DDT

Chloroform

Gold

Platinum

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Chlorine

Uses of chlorine

Preparation of poisonous gases

Mustard gas (ClCH₂CH₂SCH₂CH₂Cl)

Tear gas

(CCl₃NO₂)

Phosgene (COCl₂)

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12C07.1

CV 4

Hydrogen Chloride

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12C07.5 Group 17 Elements – The Halogen Family

Hydrogen chloride, HCl

Prepared by Glauber in 1648

Humphry Davy told it is a compound of H and Cl

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12C07.5 Group 17 Elements – The Halogen Family

NaCl + H₂SO₄ NaHSO₄ + HCl

420 K

NaHSO₄ + NaCl Na₂SO₄ + HCl

420 K

Gas jar

HCl Gas

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12C07.5 Group 17 Elements – The Halogen Family

Properties of hydrogen chloride

Physical properties

Chemical properties

Colourless gas
Pungent smelling
Colourless in liquid state
White in crystalline state
Extremely soluble in water

Ionizes in water
Reaction with ammonia
Formation of aqua regia
Reaction with salts of weaker acids

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12C07.5 Group 17 Elements – The Halogen Family

Chemical Properties of hydrogen chloride

HCl gas

Ionization in water

H⁺ ion

H₃O⁺ ion

H₂O

K_a =10⁷

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12C07.5 Group 17 Elements – The Halogen Family

Chemical Properties of hydrogen chloride

Reaction with ammonia

NH₃

HCl

White and dense fumes of NH₄Cl

Base

Acid

Salt

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12C07.5 Group 17 Elements – The Halogen Family

Chemical Properties of hydrogen chloride

Formation of aqua regia

1 vol. conc. HNO₃

3 vol. conc. HCl

Aqua regia

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12C07.5 Group 17 Elements – The Halogen Family

Chemical Properties of hydrogen chloride

Reaction with salts of weaker acids

Salt of carbonic acid

Salt of sulphuric acid

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12C07.5 Group 17 Elements – The Halogen Family

Uses of hydrogen chloride

Manufacture of chlorine, NH4Cl and glucose
Extracting glue from bones and purifying bone black
In medicine and as a laboratory reagent

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12C07.5 Group 17 Elements – The Halogen Family

Q. When HCl reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Why?

Sol.

FeCl₃

Reducing agent

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12C07.1

CV 5

Oxoacids of Halogens

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12C07.5 Group 17 Elements – The Halogen Family

Oxoacids of Halogens

Contain oxygen, hydrogen and other non metallic element

Halic (I) acid �(Hypohalous acid)
Halic (III) acid �(Halous acid)
Halic (V) acid �(Halic acid)
Halic (VII) acid �(Perhalic acid)


– �–
– �–
– �–


– �–


–�–

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12C07.5 Group 17 Elements – The Halogen Family

Oxoacids of Halogens

Nomenclature

-ous

Chlorous acid

-ic

Chloric acid

Hypo - ous

Hypochlorous acid

Per - ic

perchloric acid

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12C07.5 Group 17 Elements – The Halogen Family

Oxoacids of Chlorine

Chlorous acid

Chloric acid

Hypochlorous acid

Perchloric acid

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12C07.1

CV 4

Interhalogen Compounds

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12C07.5 Group 17 Elements – The Halogen Family

Xʹ

Interhalogen compounds

Xʹ

Larger in size

Smaller in size

More electropositive

Less electropositive

XXʹ

XXʹ₃

XXʹ₅

XXʹ₇

Bent ‘T’ shape

Square pyramidal

Pentagonal bipyramidal

Linear

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12C07.5 Group 17 Elements – The Halogen Family

Preparation of Interhalogen compounds

Equal volume

Excess

Diluted

Equimolar

Excess

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Type	Formula	Physical state and column	Structure
		Colourless gas
		Pale brown gas
		Detected spectroscopically
		Gas

		Black solid
		Colourless gas	Bent T – shaped
		Yellow green liquid	Bent T – shaped
		Yellow powder	Bent T – shaped (?)
		Orange solid	Bent T – shaped (?)
			Square Pyramidal
		Colourless liquid	Square
		Colourless liquid	Pyramidal
		Colourless gas	Pentagonal

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12C07.5 Group 17 Elements – The Halogen Family

Physical properties of Interhalogen compounds

Covalent molecules

Diamagnetic in nature

Volatile solids or liquids at 298 K except ClF(g)

Physical properties are intermediate between those of constituent halogens

m.p. and b.p. are a little higher than expected

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12C07.5 Group 17 Elements – The Halogen Family

Chemical properties of Interhalogen compounds

Fluorine

Xʹ

Chemical reactivity

Interhalogen

Other halogen

Weak bond

Strong bond

Inter electronic repulsion

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12C07.5 Group 17 Elements – The Halogen Family

Chemical properties of Interhalogen compounds

Hydrolysis

XXʹ

XXʹ₃

XXʹ₅

XXʹ₇

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12C07.5 Group 17 Elements – The Halogen Family

Sol.

VSEPR theory

bp-bp < lp-bp > lp-lp

No repulsion

bp-bp

bp-lp

lp-lp = 0

lp-bp = 4

bp-bp = 2