11C10�
The s – Block Elements
s - block
Alkali metals
Alkaline earth metals
11C10.1��Group 1 Elements : Alkali Metals
Learning Objectives
Introduction
General Trends in Some properties
Properties of Group 1 Elements
Anomalous Behaviour of Lithium
11C10.1 Group 1 Elements : Alkali Metals
11C10.1
CV 1
Introduction
Abundant
Low in abundance
Radioactive
Longest-lived isotope
Half life of 21 minutes
Electronic Configuration
Lithium
Sodium
Potassium
Rubidium
Caesium
Francium
Readily lose electron
Electronic Configuration
Lithium
Sodium
Potassium
Rubidium
Caesium
Francium
Readily lose electron
Electronic Configuration
Lithium
Sodium
Potassium
Rubidium
Caesium
Francium
Never found in free state in nature
Readily lose electron
11C10.1
CV 2
General Trends in Some properties
Metallic And Ionic Radius
Monovalent ion are smaller than parent ion
Increase in size while going from Li to Cs
Li
Na
K
Rb
Cs
Ionization Enthalpy
Decrease down the group from Li to Cs
Outermost electron is very well screened from the nuclear charge
Increasing size outweighs the nuclear charge
Li
Na
K
Rb
Cs
Fr
Hydration Enthalpy
Decrease with increase in ionic sizes :
highest degree of hydration
ConcepTest
Ready for Challenge
Q. Explain why is sodium less reactive than potassium.
Pause the video
Time duration: 1 minute
Q. Explain why is sodium less reactive than potassium.
Sol.
Since ionization enthalpy of potassium is less than that of sodium
More reactive
11C10.1
CV 3
Properties of Group 1 Elements
Physical Properties
Alkali metals are silvery white, soft and light metals
Because of large size, these elements have low density
which increases down the group from Li to Cs
Flame Test
The alkali metals and their salts impart characteristic colour to an oxidising flame.
Lithium
Sodium
Potassium
Rubidium
Caesium
Crimson red
Violet
Yellow
Red violet
Blue
Heat from the flame excites outermost orbital electron to a
higher energy level
Chemical Properties
Highly reactive due to their large size and low ionization enthalpy
Reactivity increases down the group
Lithium
Sodium
Potassium
Must be stored in saturated organic oil
(They may even react with water in air)
Chemical Properties
Reactivity towards air
Alkali metal
Tarnished
alkali metal
air
Oxide
Peroxide
Superoxide
Oxidation state of alkali metal is +1
Chemical Properties
Reactivity towards air
Alkali metal
Tarnished
alkali metal
air
Exceptional behaviour
Chemical Properties
Reactivity towards water
Hydroxide
Dihydrogen
Chemical Properties
Reactivity towards water
Hydroxide
Dihydrogen
Small size and
very high hydration energy
Chemical Properties
Reactivity towards water
Hydroxide
Dihydrogen
Small size and
very high hydration energy
Also react with proton donor such as alcohol, gaseous ammonia and alkynes
Chemical Properties
Reactivity towards dihydrogen
Ionic solids
High melting point
Reactivity towards halogens
Covalent
High polarization capability of Lithium ion
Among halides, Lithium Iodide is the most covalent in nature
Thermal stability :
Reducing nature
The alkali metals are strong reducing agents
With the small size of its ion, lithium has the highest hydration enthalpy
High reducing power
Chemical Properties
Solutions in liquid ammonia
Chemical Properties
Solutions in liquid ammonia
The blue colour of the solution is due to the ammoniated electron which absorbs energy in visible region of light
Chemical Properties
Solutions in liquid ammonia
The solutions are paramagnetic and standing slowly liberate hydrogen resulting in amide formation
Chemical Properties
Solutions in liquid ammonia
The solutions are paramagnetic and standing slowly liberate hydrogen resulting in amide formation
Chemical Properties
Solutions in liquid ammonia
The solutions are paramagnetic and standing slowly liberate hydrogen resulting in amide formation
‘am’ denotes solution in ammonia
In concentrated solution,
Chemical Properties
Solutions in liquid ammonia
The solutions are paramagnetic and standing slowly liberate hydrogen resulting in amide formation
In concentrated solution,
Diamagnetic
‘am’ denotes solution in ammonia
Chemical Properties
11C10.1
PSV 1
Pause the video
Time duration : 3 minutes
Q.
Give reasons:
Sol.
Q.
Give reasons:
Higher charge
Greater polarising power
Covalent
Bigger size
More polarisable
Covalent
Lower M.P.
small size
high polarising power
soluble in alcohol
11C10.1
CV 4
General Characteristics of the Compounds of the Alkali Metals
Oxides and Hydroxides
Increasing stability, as the size of the metal ion increases, is due to the stabilisation of large anions by larger cations through lattice energy effects
On combustion of excess air,
Oxides and Hydroxides
On combustion of excess air,
These oxides are easily hydrolysed by water to form the hydroxides according to the following reactions :
White crystalline solids
Strongest of all bases and dissolve freely in water
With evolution of much heat
Colourless when pure
Yellow or orange
Halides
High melting point
Colourless crystalline solids
Prepared by reaction of the oxide, hydroxide or carbonate with aqueous hyrohalic acid(HX)
Melting and Boiling points always follow the trend :
fluoride > chloride > bromide > iodide
All these halides are soluble in water
Halides
Less negative
Less negative
Salts of Oxo-acids
Oxo-acids are those in which the acidic proton is on a hydroxyl group with an oxo-group attached to the same atom
The alkali metals form salts with all the oxo - acids
They are generally soluble in water and thermally stable
Highly stable to heat
As the electropositive character increases down the group, the stability of
the Carbonates And hydrogencarbonates increases
Salts of Oxo-acids
Not very stable to heat
Small size
Large
Does not exist as a solid
11C10.1
PSV 2
Q.
Pause the video
Time duration : 2 minutes
Sol.
Q.
11C10.1
CV 5
Anomalous Behaviour of Lithium
Exhibit some properties which are
Different from respective group members
Anomalous Properties of Lithium
Anomalous Properties of Lithium
The anomalous behaviour of lithium is due to the :
As a result,
There is increased covalent character of lithium compounds
which is responsible for their solubility in organic solvents
Difference between Lithium and Alkali Metals
Lithium is much harder. Its M.P. and B.P. are higher than the other alkali metals
Least reactive but the strongest reducing agent among all the alkali metals
On combustion in air -
Unlike other alkali metals
Difference between Lithium and Alkali Metals
Other alkali metal chlorides do not form hydrates
Difference between Lithium and Alkali Metals
Not obtained in solid form
Obtained in solid form
Diagonal Relationship
Diagonal Relationship
Similarities between Lithium and Magnesium
The similarity between lithium and magnesium is particularly striking and arises because of their small size
Both are harder and lighter than other elements in the respective groups
Lithium
Magnesium
Similarities between Lithium and Magnesium
Both react slowly with water
Their oxides and hydroxides are much less soluble and their hydroxides decompose on heating
Both form Nitrides :
Similarities between Lithium and Magnesium
ConcepTest
Ready for Challenge
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Time duration: 1 minute
Sol.
Summary
Metal | | | | | |
Colour | Crimson red | Yellow | Violet | Red Violet | Blue |
| | | | | |
Summary
Group-1 (M)
11C10.1 Group 1 Elements : Alkali Metals
Reference Questions
NCERT Exercise Questions: 10.1, 10.3, 10.4, 10.5, 10.7, 10.9, 10.10, 10.12, 10.13,
10.14, 10.22, 10.23, 10.25, 10.28, 10.30, 10.31
NCERT In-Text Questions: 10.1, 10.2, 10.3
Workbook Questions: 1, 2, 3, 4, 11, 12, 13, 16, 17, 19
11C10.2��Some Important Compounds of Alkali Metals
Learning Objectives
Washing Soda
Caustic soda And Baking Soda
Common salt
Biological Importance of Sodium and Potassium
11C10.2 Some Important Compounds of Alkali Metals
11C10.2
CV 1
Washing Soda
Sodium Carbonate ( Washing Soda)
Prepared by Solvay process
The equations for the complete process
maybe written as :
Sodium Carbonate ( Washing Soda)
These are heated to give sodium carbonate :
Prepared by Solvay process
Properties of Sodium Carbonate
Also called washing soda
Readily soluble in water
Carbonate part of sodium carbonate gets hydrolysed by water to form an alkaline solution
Uses of Sodium Carbonate
It is used in water softening, laundering and cleaning
Used in the manufacture of glass, soap, borax and caustic soda :
Glass
Soap
Uses of Sodium Carbonate
Important laboratory reagent both in qualitative and quantitative analysis
Paper industry
Paint industry
Textile industry
11C10.2
PSV 1
Q.
Why is Potassium Carbonate not prepared through Solvay Process ?
Pause the video
Time duration : 2 minutes
Sol.
Potassium hydrogencarbonate is too soluble to be precipitated by the addition of ammonium hydrogencarbonate to a saturated solution of potassium chloride
Q.
Why is Potassium Carbonate not prepared through Solvay Process ?
Does not Precipitate
11C10.2
CV 2
Caustic Soda and Baking Soda
Sodium hydroxide is generally prepared commercially by the electrolysis of sodium chloride in Castner-kellner cell
Castner- Kellner Cell
Brine solution
Mercury
Water
The amalgam is treated with water to give sodium hydroxide and hydrogen gas
White translucent solid
Readily soluble in water
strong alkaline solution
deliquescent
Uses
Manufacture of :
Artificial silk
Soap
Paper
Number of chemicals
Uses
Petroleum refining
Purification of bauxite
Textile industries
Pure fats and oils
Laboratory reagent
Also known as baking soda because it decomposes on heating to generate bubbles of carbon dioxide
Skin infection
Fire extinguisher
11C10.2
CV 3
Common Salt
Obtained from sea water
In tropical countries like India, common salt is generally obtained by evaporation of sea water
Approximately 50 lakh tons of salt are produced annually in India by solar evaporation
Crude sodium chloride :
deliquescent
Crude sodium chloride is dissolved in minimum amount of water
Filtration to remove insoluble impurities
The solution is then saturated with hydrogen chloride
Crystals of pure sodium chloride separate out
Calcium and Magnesium chloride, being more soluble than sodium chloride, remain in water
The solubility does not increase appreciably with increase in temperature
Uses
11C10.2
PSV 2
Q.
Starting with sodium chloride how would you proceed to prepare -
Pause the video
Time duration : 2 minutes
Sol.
11C10.2
CV 4
Biological Importance of
Sodium and Potassium
Biological Importance
Transmission of nerve signals
Regulating the flow of water across cell membrane
Transport of sugars and amino acids into cells
Biological Importance
Sodium and potassium, although so similar chemically, differ quantitatively -
Extracellular space
Intracellular space
Activate many enzymes
Participate in the oxidation of glucose
to produce ATP
With sodium, are responsible for transmission of nerve signals
Biological Importance
Extracellular space
Intracellular space
As a typical example in blood plasma
Biological Importance
Which consumes more than on third of the ATP used by resting animal
sodium potassium Pump
cell membranes
about 15kg per 24hrs in resting human
Biological Importance
Summary
Reference Questions
NCERT Exercise Questions: 10.16, 10.27
11C10.2 Some Important Compounds of Alkali Metals
11C10.3��Group 2 Elements : Alkaline �Earth Metals
Learning Objectives
General Trends in properties of Alkaline Earth Metals
Properties of Group 2 Elements
Anomalous Behaviour of Beryllium
11C10.3 Group 2 Elements : Alkaline Earth Metals
11C10.3
CV 1
General Trends in Properties
Of
Alkaline Earth Metals
Introduction
These elements have two electrons in the s-orbital of the valence shell
Beryllium
Magnesium
Calcium
Strontium
Barium
Radium
Rare earth metal
Fifth
Sixth
Low abundance
Rarest of all
Atomic and Ionic Radii
Within the group, the atomic and ionic radii increase with increase in atomic number
Due to the increased nuclear charge in these elements
Atomic and Ionic radius of alkaline earth metals are smaller than those of the corresponding alkali metals in the same period
Ionisation Enthalpies
Low ionization enthalpies due to fairly large size of the atoms
Since the atomic size increases down the group, their ionization enthalpies decreases
Due to their small size as compared to the corresponding alkali metals
Hydration Enthalpies
Decrease with increase in ionic size down the group :
Larger than those of alkali metal ions
more extensively hydrated
Do not form such hydrates
ConcepTest
Ready for Challenge
Q. Property of alkaline earth metals that increases with their atomic
number:
Pause the video
Time duration: 1 minute
a) Solubility of their hydroxides in water
Sol.
Q. Property of alkaline earth metals that increases with their atomic
number:
a) Solubility of their hydroxides in water
Solubility of the hydroxide increases as their hydration energies are more than their lattice energies
Hence, option a) is correct
11C10.3
CV 2
Properties of Group 2 Elements
Physical Properties
The alkaline earth metals,
Silvery white
Lustrous
Relatively soft but harder than the alkali metal
M.P and B.P of these metals are higher than the corresponding alkali metals due to smaller sizes
Magnesium and Beryllium appear to be somewhat greyish
Physical Properties
Calcium
Strontium
Barium
Brick red
Crimson
Apple-green
electrons are excited to higher energy levels
when they drop back to the ground state
energy is emitted in the form of visible light
Physical Properties
Calcium
Strontium
Barium
Brick red
Crimson
Apple-green
The electrons in beryllium and magnesium are too strongly bound to get excited by flame
High electrical and thermal conductivities
Chemical Properties
Less reactive than the alkali metals
Reactivity towards Air and Water
Oxide film
Beryllium and Magnesium are Less reactive to oxygen and water
Reactivity of these elements increases on going down the group
Chemical Properties
Less reactive than the alkali metals
Reactivity of these elements increases on going down the group
Reactivity towards Air and Water
Powdered beryllium burns brilliantly on ignition in air
Chemical Properties
Less reactive than the alkali metals
Reactivity towards Air and Water
Magnesium is more electropositive
Burns with dazzling brilliance in air
Reactivity of these elements increases on going down the group
Chemical Properties
Less reactive than the alkali metals
Reactivity towards Air and Water
Calcium, Strontium and Barium are readily attacked by air to form
the oxide and nitride
Also react with water with increasing vigour even in cold
To form hydroxides
Reactivity of these elements increases on going down the group
Chemical Properties
Reactivity towards Halogens
Combine with halogen at elevated temperatures forming their halides
Chemical Properties
Reactivity towards Hydrogen
Reactivity towards acids
Readily react with acids liberating dihydrogen
Chemical Properties
Reducing Nature
Strong reducing agents
Large negative values of their reduction potential
Their reducing power is less than those of their corresponding alkali metals
Element | | | | | | |
| | | | | | |
Less negative value
Its reducing nature is due to :
11C10.3
PSV 1
Q.
Pause the video
Time duration : 2 minutes
Sol.
Q.
Hence, Option (a) is correct
11C10.3
CV 4
General Characteristics of the Compounds of the Alkaline Metals
Chemical Properties
Form compounds which are predominantly ionic
Due to increased nuclear charge and smaller size
more covalent
Oxides and Hydroxides
Rock salt
covalent nature
The enthalpies of formation of these oxides are quite high and consequently they are very stable to heat
Solubility
Thermal stability
Basic character
Oxides and Hydroxides
Less basic and less stable than alkali metal hydroxides
Beryllium hydroxide is amphoteric in nature as it reacts with acid and alkali both
Beryllate ion
Halides
Except for Beryllium halides, all other halides of alkaline earth metals are ionic in nature
Beryllium halides are essentially covalent and soluble in organic solvent
dissociates into the linear monomer at high temperatures of the order of 1200K
Halides
The tendency to form halide hydrates gradually decreases down the group
Salts of Oxoacids
The alkaline earth metals also form salts of oxoacids
Carbonates
Carbonates of alkaline earth metals are insoluble in water
Can be precipitated by :
Soluble salts of
group 2 metals
All the carbonates decompose on heating to give carbon dioxide and the oxide
Salts of Oxoacids
Solubility decreases
Beryllium carbonate
Salts of Oxoacids
Solubility decreases
The thermal stability increases with increasing cationic size
Beryllium carbonate
Salts of Oxoacids
Sulphates
| | |
| | |
Beryllium sulphate
Magnesium sulphate
Calcium sulphate
Strontium sulphate
Barium sulphate
Salts of Oxoacids
Sulphates
Therefore there sulphates are soluble in water
Salts of Oxoacids
Nitrates
All of them decompose on heating to give the oxide like lithium nitrate
ConcepTest
Ready for Challenge
Pause the video
Time duration: 1 minute
a) Are hygroscopic in nature
Q.
Sol.
a) Are hygroscopic in nature
Q.
Halides of alkaline earth metals are hygroscopic in nature. Therefore, their anhydrous salt are used as dehydrating agent
Hence, (d) is correct option
11C10.3
CV 5
Anomalous Behaviour of Beryllium
Exhibit some properties which are
Different from respective group members
Anomalous Behaviour of Beryllium
Anomalous Behaviour of Beryllium
Beryllium shows anomalous behaviour as compared to magnesium and rest of the members
Beryllium has exceptionally small atomic and ionic sizes and
Because of its small size it forms compounds which are largely covalent and get easily hydrolysed
Amphoteric nature
Anomalous Behaviour of Beryllium
Beryllium does not exhibit coordination number more than four
In its valence shell there are only four orbitals
The remaining members of the group can have a coordination number of six by making use of d-orbitals
Diagonal Relationship
Diagonal Relationship
Diagonal Relationship Between Beryllium and Aluminium
Like aluminium, Beryllium is not readily attacked by acids
Oxide film
Diagonal Relationship Between Beryllium and Aluminium
Beryllium hydroxide dissolves in excess of alkali to give beryllate ion,
Diagonal Relationship Between Beryllium and Aluminium
Both the chlorides are soluble in organic solvents and are strong lewis acids
They are used as Friedel craft catalyst
ConcepTest
Ready for Challenge
Pause the video
Time duration: 1 minute
Q.
a) Forming covalent compounds
in compounds
Sol.
Q.
a) Forming covalent compounds
in compounds
Max covalency : 6
Max covalency : 4
Hence, (c) is correct option
Summary
Summary
carbon
sulphur
air
(Hydrides)
acids
Reference Questions
NCERT Exercise Questions: 10.2, 10.6, 10.8, 10.11, 10.15, 10.19, 10.20, 10.29, 10.32
Workbook Questions: 5, 6, 8, 9, 14, 18, 20
11C10.3 Group 2 Elements : Alkaline Earth Metals
11C10.4��Some Important Compounds of Calcium
Learning Objectives
Quick lime and slaked lime
Calcium carbonate and Calcium sulphate
Cement
Biological Importance of Magnesium and Calcium
11C10.4 Some Important Compounds of Calcium
11C10.4
CV 1
Quick lime and Slaked lime
Removed to proceed the reaction to completion
Calcium oxide is a white amorphous solid
On exposure to atmosphere, it absorbs moisture and carbon dioxide
The addition of limited amount of water breaks the lump of lime
This process is called slaking of lime
Quick lime slaked with soda gives soda lime
Being a basic oxide, it combines with acidic oxides at high temperature
Manufacturing of cement and is the cheapest form of alkali
Manufacture of sodium carbonate from caustic soda
Purification of sugar
Manufacturing of dye stuff
White, amorphous powder
Sparingly soluble in water
White, amorphous powder
Sparingly soluble in water
Limewater: Aqueous solution of Calcium hydroxide
White, amorphous powder
Sparingly soluble in water
Limewater: Aqueous solution of Calcium hydroxide
Milk of lime: Suspension of calcium hydroxide in water
Milk of lime reacts with Chlorine to form hypochlorite, a constituent of bleaching powder:
Bleaching powder
Calcium
hydrogencarbonate
Uses of Calcium Hydroxide
| | |
| | |
Mortar
Purification of sugar
White wash
Making of glass
Tanning of leather
Bleaching powder
ConcepTest
Ready for Challenge
Pause the video
Time duration: 1 minute
Q.
Sol.
Q.
Heat
Calcium Carbonate
Calcium Oxide
Calcium Oxide
Calcium Hydroxide
Calcium Hydroxide
Bleaching Powder
11C10.4
CV 2
Calcium Carbonate and
Calcium Sulphate
Occurs in nature in several forms like -
Limestone
Marble
Chalk
Can be prepared by -
Slaked lime
Calcium
chloride
Sodium
carbonate
White fluffy powder
Almost insoluble in water
It reacts with dilute acid to liberate carbon dioxide
Uses of Calcium Carbonate
Building material in the form of Marble
manufacture of quick lime
Extraction of Iron
Calcium carbonate and Magnesium carbonate are used as a flux
Uses of Calcium Carbonate
| |
Antacid
| | |
Abrasive in toothpaste
Consituent of Chewing gum
Filler in cosmetic
It is a hemihydrate of Calcium sulphate
Above 393K,
no water of crystallisation is left and anhydrous calcium sulphate is formed
Dead burnt plaster
Remarkable property of setting with water
On mixing with adequate amount of water
Forms a plastic mass
Gets into hard solid in 5-15 mins
Uses of Calcium Sulphate
| |
| |
Mostly used in building industry as well as plasters
For immobilising the affected part of organ
Where there is bone fracture
Used for making sculptures
Used in dentistry
11C10.4
PSV 1
Q.
Heat
Strongly Heated
Sol.
Heat
Strongly
Heat
Plaster of Paris
Dead burn Plaster
Lime
11C10.4
CV 3
Cement
Cement
Joseph Aspdin
Also called Portland cement
Resembles with the natural limestone quarried in the Isle of Portland, England
Cement is a product obtained by combining a material rich in :
lime
Cement
Average composition of Portland cement is -
| | | | | |
| | | | | |
Good Quality cement
Good Quality cement
Cement
Cement
Important ingredient of Portland Cement -
Setting of Cement – Hydration of molecules and their rearrangement
Gypsum is added to slow down the process of setting of cement
ConcepTest
Ready for Challenge
State whether the following is true or false :
Pause the video
Time duration: 1 minute
Q.
Sol.
State whether the following is true or false :
Q.
11C10.4
CV 4
Biological Importance of
Magnesium and Calcium
Biological Importance of Magnesium and Calcium
Daily requirement in the human body is estimated to be 200-300mg
Biological Importance of Magnesium
All the enzyme that utilise ATP in phosphorous transfer require magnesium as a cofactor
Chlorophyll contains Mg
Biological Importance Calcium
Plays an important role in neuromuscular function, interneuronal transmission, cell membrane integrity and blood coagulation
Maintained by -
Calcitonin and Parathyroid hormone
Biological Importance of Magnesium and Calcium
Did you know
Biological Importance of Magnesium and Calcium
400mg per day
Calcium
Did you know
Plasma
Summary
Summary
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Reference Questions
NCERT Exercise Questions: 10.17, 10.21, 10.24
Workbook Questions: 7, 10, 15
11C10.4 Some Important Compounds of Calcium