IMPORTANT DIAGRAMS��CHEMISTRY

Class :- X

Subject :- Science

Name of Teacher :- Mr. Satish Kumar (PGT Chem)

School :- KV RRL Jorhat, Assam

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Chemical reactions and equations

• 1) Electrolysis of water :-
• If electric current is passed through water, it splits up into hydrogen and oxygen.
• 2H₂O 2H₂ + O₂

Electric current

2) Displacement reaction :-

• Iron displaces copper from copper sulphate solution to form iron sulphate and copper. The blue colour of copper sulphate changes to green iron sulphate.
• Fe + CuSO₄ FeSO₄ + Cu

after 15 – 20 minutes

3) Acid solution conducts electricity :-

• If electric current is passed through dilute HCl solution, the bulb glows. This shows that acid solution conducts electricity.

Beaker

Battery

Dilute HCl

solution

Iron nails

Bulb

4) pH of some common solutions on a pH paper :-

Metals and non metals

• 1) Metals are good conductors of heat :-

Conduction of heat

Heat

Wax pieces

Aluminium strip

2) Metals are good conductors of electricity :-

• Set up a simple electric circuit as shown. Place the metal to be tested between the terminals A and B. If the bulb glows, it shows that the metal is a conductor of electricity.

A

B

3) Testing conductivity of a salt solution :-

Molten sodium chloride conducts electricity

4) Reactivity series of metals :-

• The arranging of metals in the decreasing order of their reactivity is called reactivity series of metals.
• K - Potassium Most reactive
• Na - Sodium
• Ca - Calcium
• Mg - Magnesium
• Al - Aluminium
• Zn - Zinc Reactivity decreases
• Fe - Iron
• Pb - Lead
• H - Hydrogen
• Cu - Copper
• Hg - Mercury
• Ag - Silver
• Au - Gold Least reactive

5) Steps involved in the extraction of metals from their ores :-

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• Metals of Metals of Metals of
• high reactivity medium reactivity low reactivity

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• Electrolysis of
• molten ore Carbonate ore Sulphide ore Sulphide ore

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• Pure metal Calcination Roasting Roasting

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• Oxide of metal Metal

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• Reduction to metal Refining

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• Refining

Ore

6) Extraction of metals at the top of the activity series :-

• Metals at the top of the activity series like K, Na, Ca, Al etc. cannot be obtained from their ores by simple heating or by heating with reducing agents. They are obtained by electrolytic reduction of their molten chlorides.
• Eg :- When electric current is passed through molten sodium chloride, sodium metal is deposited at the cathode and chlorine gas is deposited at the anode.
• At cathode :- Na ⁺ + e ^- Na (Sodium metal)
• At anode :- 2Cl ^- Cl₂ + 2e ^- (Chlorine gas)

7) Refining of metals :-

• The removal of impurities from the metal to obtain the pure metal is called refining of metals. The most common method for refining of metals is electrolytic refining.
• In this method a block of the impure metal is made the anode and a thin sheet of the pure metal is made the cathode. The electrolyte is a salt solution of the metal to be purified.
• Eg :- In the electrolytic refining of copper, a block of impure copper is made the anode and a thin sheet of pure copper is made the cathode. The electrolyte is acidified copper sulphate solution. When electric current is passed through the electrolyte, pure copper from the anode is deposited at the cathode and the impurities settle down as anode mud.

8) Corrosion :-

• Corrosion is the damage caused to metals due to the reaction of metals with oxygen, moisture, carbon dioxide etc.
• Eg :- Formation of brown coating of rust over iron.
• Formation of green coating of basic copper carbonate over copper.
• Formation of black coating of silver sulphide over silver.
• To show that air and moisture are necessary for the rusting of iron :-
• Take three test tubes marked 1,2,3 and put iron nails in each of them. Put some anhydrous calcium chloride in test tube 1 to absorb moisture. Pour some boiled distilled water in test tube 2 and pour some oil over it to prevent air into the test tube. Pour some water in test tube 3. Cork the test tubes and leave them for a few days. The nails in test tube 1 does not get rusted because it had only air and no water. The nails in test tube 2 does not rust because it had only water and no air. The nails in test tube 3 gets rusted because it had air and water.

Carbon and its compounds

• 1) Covalent bonds :- Covalent bond is chemical bond formed by the sharing of electrons between atoms.
• The sharing of one pair of electrons results in the formation of single
• covalent bond, sharing of two pairs of electrons results in the formation
• of double covalent bond and sharing of three pairs of electrons results
• in the formation of triple covalent bond.
• Eg :- Formation of single covalent bond in Hydrogen
• molecule - H₂
• The atomic number of hydrogen is 1, its electronic arrangement is 1, it
• has 1 valence electron. It needs 1 electron more to attain stability. So
• two hydrogen atoms share 1 pair of electrons resulting in the formation
• of a single covalent bond in hydrogen molecule H_2.

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• H x + x H H X X H H – H H₂

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Formation of double covalent bond in oxygen molecule-O₂

• The atomic number of oxygen is 8, its EC is 2,6, it has 6 VE, it needs 2 electrons more to attain stability. So two oxygen atoms share two pairs of electrons resulting in the formation of a double covalent bond in oxygen molecule O₂

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• O + O O O O = O O₂

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• Formation of triple covalent bond in Nitrogen molecule - N₂
• The atomic number of nitrogen is 7, its EC is 2,5, it has 5 VE, it needs 3 electrons more to attain stability. So two nitrogen atoms share three pairs of electrons resulting in the formation of a triple covalent bond in nitrogen molecule N₂

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• N + N N N N Ξ N N₂

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2) Electron dot structures :-

• Methane molecule – CH₄ Ethane molecule – C₂H₆

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• H H H

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• H C H H C C H
• H H H

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• H H H
• I I I
• H – C – H H – C – C – H
• I I I
• H H H

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3) Formation of a very large number of carbon compounds :-

• Carbon forms a very large number of compounds. The number of carbon compounds is more than three million. It is more than the number of compounds formed by all other elements. This is because :-
• i) Carbon atom can form bonds with other carbon atoms to form long
• chains, branched chains and closed rings. This property is called
• catenation.
• ii) Since the valency of carbon is 4, it can form bonds with other
• carbon atoms or with atoms of other elements like hydrogen,
• oxygen, nitrogen, halogens etc.
• I
• C
• I I I I I I I I I I C
• C – C – C – C – C – C C – C – C – C C C
• I I I I I I I I I I C C
• C C
• I
• Long chain Branched chain Closed ring

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4) Formation of a very large number of carbon compounds :-

• Carbon forms a very large number of compounds. The number of carbon compounds is more than three million. It is more than the number of compounds formed by all other elements. This is because :-
• i) Carbon atom can form bonds with other carbon atoms to form long
• chains, branched chains and closed rings. This property is called
• catenation.
• ii) Since the valency of carbon is 4, it can form bonds with other
• carbon atoms or with atoms of other elements like hydrogen,
• oxygen, nitrogen, halogens etc.
• I
• C
• I I I I I I I I I I C
• C – C – C – C – C – C C – C – C – C C C
• I I I I I I I I I I C C
• C C
• I
• Long chain Branched chain Closed ring

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5) Isomerism :-

• Carbon compounds having the same molecular formula but different structural formulae are called isomers. This property is called isomerism.
• Eg:- Butane – C₄H₁₀ has 2 isomers. They are Normal butane and Iso butane.
• H H H H H H H
• I I I I I I I
• H – C – C – C – C – H H – C – C – C – H Iso butane
• I I I I I I
• H H H H H H
• H – C – H
• Normal butane I
• H
• Pentane – C₅H₁₂ has 3 isomers. They are Normal pentane, Iso pentane and Neo
• pentane. Neo pentane
• Iso pentane H
• H I
• I H – C – H
• Normal pentane H – C – H H H
• I I
• H H H H H H H H H – C – C – C – H
• I I I I I I I I I I
• H – C – C – C – C – C – H H – C – C – C – C – H H H
• I I I I I I I I I H – C – H
• H H H H H H H H H I
• H

6) Functional groups :-

• An atom or a group of atoms which decides the properties of a carbon compound is called a functional group.
• i) Halide ( Halo group) :- - Cl, - Br, etc. ( Names end with – ane )
• Eg :- CH₃Cl – Chloro methane, C₂H₅Br – Bromo ethane

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• ii) Alcohol :- - OH ( Names end with – ol )
• Eg :- CH₃OH – Methanol, C₂H₅OH – Ethanol
• H
• iii) Aldehyde :- - CHO - C ( Names end with – al )
• O
• Eg :- HCHO – Methanal, CH₃CHO – Ethanal
• O
• II
• iv) Carboxylic acid :- - COOH - C - OH (Names end with – oic acid )
• Eg :- HCOOH – Methanoic acid, CH₃COOH – Ethanoic acid
• v) Ketone :- - CO - C - (Names end with – one )
• II
• O
• Eg :- CH₃COCH₃ – Propanone , CH₃COC₂H₅ - Butanone

7) Soaps and detergents :-

• a) Soaps :- Soaps are long chain sodium or potassium salts of carboxylic acids. Eg:- Sodium stearate – C₁₇H₃₅COONa
• Structure of soap molecule :- A soap molecule has two parts. A long hydrocarbon part which is hydrophobic (water repelling) and soluble in oil and grease and a short ionic part which is hydrophyllic (water attracting) and insoluble in oil and grease.
• COO Na ⁺
• Hydrocarbon part Ionic part
• (Water repelling) (Water attracting)
• Cleansing action of soap :- When soap is dissolved in water it forms spherical structures called micelles. In each micelle the soap molecules are arranged radially such that the HC part is towards the centre and the ionic part is towards the outside. The HC part dissolves the dirt, oil and grease and forms an emulsion at the centre of the micelles which can be washed away by water.

Periodic classification of elements

• 1) Doberiener’s Triads :- Dobereiner classified elements in the increasing order of their atomic masses into groups of three elements called triads. In each triad the atomic mass of the middle element was approximately equal to the average atomic mass of the other two elements.
• The defect in this classification was that all the then known elements could not be correctly arranged into triads.

2) Newland’s octaves :-

• Newland classified the elements in the increasing order of their atomic masses into groups of eight elements called octaves like the notes of music. He found that when the elements were arranged in the increasing order of their atomic masses into octaves then there was similarity of properties in every eighth element.

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• The defect in this classification was:-
• i) All the known elements and elements discovered later could not be correctly arranged into octaves.
• ii) Some elements having different properties were placed in the same groups like cobalt and nickel having different properties are placed along with Fluorine, Chlorine and Bromine. Some elements having similar properties are placed in different groups like Iron having properties similar to Cobalt and Nickel are placed in different rows.

3) Mendeleev’s periodic law :-

• Mendeleev’s periodic law states that, ‘ The properties of elements are periodic functions of their atomic masses’.

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A B

A B

A B

A B

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A B

Transition series

4) Modern periodic law :-

• Modern periodic law states that, ‘ The properties of elements are periodic functions of their atomic numbers’.

5. Properties of elements in periods and groups :-

• i) Valence electrons :-
• In a period the number of valence electrons increases from 1 to 8 from the left to the right and the number of shells is the same.
• Eg :- 2^nd Period
• Elements - Li, Be, B, C, N, O, F, Ne
• AN - 3 4 5 6 7 8 9 10
• EC - 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8
• Valence electrons - 1 2 3 4 5 6 7 8
• Shells - 2 2 2 2 2 2 2 2
• In a group the number of valence electrons is the same for all the elements but the number of shells increases from top to bottom.
• Eg :- Group – IA
• Elements AN EC VE Shells
• H 1 1 1 1
• Li 3 2,1 1 2
• Na 11 2,8,1 1 3
• K 19 2,8,8,1 1 4

ii) Valency :-

• In a period the valency of the elements increases from 1 to 4 and then decreases from 4 to 0 from the left to the right.
• Eg :- 2^nd Period
• Elements - Li, Be, B, C, N, O, F, Ne
• AN - 3 4 5 6 7 8 9 10
• EC - 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8
• Valence electrons - 1 2 3 4 5 6 7 8
• Valency - 1 2 3 4 3 2 1 0

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• In a group the valency is the same for all elements of the group.
• Eg :- Group – IA
• Elements AN EC VE Valency
• H 1 1 1 1
• Li 3 2,1 1 1
• Na 11 2,8,1 1 1
• K 19 2,8,8,1 1 1

ii) Valency :-

• In a period the valency of the elements increases from 1 to 4 and then decreases from 4 to 0 from the left to the right.
• Eg :- 2^nd Period
• Elements - Li, Be, B, C, N, O, F, Ne
• AN - 3 4 5 6 7 8 9 10
• EC - 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8
• Valence electrons - 1 2 3 4 5 6 7 8
• Valency - 1 2 3 4 3 2 1 0

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• In a group the valency is the same for all elements of the group.
• Eg :- Group – IA
• Elements AN EC VE Valency
• H 1 1 1 1
• Li 3 2,1 1 1
• Na 11 2,8,1 1 1
• K 19 2,8,8,1 1 1

iii) Atomic size ( Radius of the atom) :-

• In a period the atomic size of the elements decreases from the left to the right because the nuclear charge (number of protons) increases and so the electrons are pulled closer to the nucleus.
• Eg :- 2^nd Period
• Elements - Li, Be, B, C, N, O, F, Ne
• AN - 3 4 5 6 7 8 9 10
• EC - 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8
• No. of protons - 3 4 5 6 7 8 9 10
• Atomic size decreases
• In a group the atomic size of the elements increases from top to bottom because the number of shells increases and the distance between the nucleus and shells also increases.
• Eg :- Group – I A
• Elements AN EC VE Shells
• H 1 1 1 1 Atomic
• Li 3 2,1 1 2 size
• Na 11 2,8,1 1 3 increases
• K 19 2,8,8,1 1 4

iv) Metallic property (Electropositive nature) :-

• In a period the metallic property of the elements decreases from the left to the right.
• Eg :- 3^rd Period
• Elements - Na, Mg, Al, Si, P, S, Cl, Ar
• Metals Metalloid Non metals
• Metallic property decreases
• In a group the metallic property of the elements increases from the top to the bottom.
• Eg :- Group VI A
• Elements
• Carbon C - Non metal Metallic
• Silicon Si - Metalloid property
• Germanium Ge - Metalloid increases
• Tin Sn - Metal
• Lead Pb - Metal

v) Non metallic property (Electronegative nature):-

• In a period the non metallic property of the elements increases from
• the left to the right.
• Eg :- 3^rd Period
• Elements - Na, Mg, Al, Si, P, S, Cl, Ar
• Metals Metalloid Non metals
• Non metallic property increases

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• In a group the non metallic property of the elements decreases from
• the top to the bottom.
• Eg :- Group VI A
• Elements
• Carbon C - Non metal Non metallic
• Silicon Si - Metalloid property
• Germanium Ge - Metalloid decreases
• Tin Sn - Metal
• Lead Pb - Metal

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