CH-3 (METALS AND NON-METALS) Class-10 | NCERT Topper Notes

Chapter-3
Metals And Non-Metals

• Elements can be classified as metals and non-metals on the basis of their properites.

• Example of some metals are :

Iron(Fe), Aluminium (Al), Silver(Ag), Copper(Cu)

• Example of some non-metals are:

Hydrogen(H), Nitrogen(N), Sulphur(S), Oxygen(O)

I. PHYSICAL PROPERTIES

PROPERTY	METALS	Non-METALS
1. Lustre	Metals have shining surface.	They do not have shining surface. • Except Iodine.
2. Hardness	They are generally hard. • Except Sodium, Lithium and Potassium which are soft and can be cut with knife.	Generally soft. • Except Diamond, a form of carbon which is the hardest natural substance.
3. State	Exist as solids. • Except Mercury.	Exist as solids or gaseous. • Except Bromine.
4. Malleability	Metals can be beaten into thin sheets. • Gold and Silver are the most malleable metals.	Non-metals are non-malleable.
5. Ductility	Metals can be drawn into thin wires.	They are non-ductile.
6. Conductor of heat & electricity.	Metals are good conductors of heat and electricity. • Silver(Ag) and Copper(Cu): Best conductors of heat. • Lead(Pb), Mercury(Hg) poor conductor of heat.	Non-meatals are poor conductor of heat and electricity. • Except Graphite.
7. Density	Generally have high density and high melting point. • Except Sodium and Potassium.	Have low density and low melting point.
8. Sonorous	Metals produce a sound on striking a hard surface.	They are not sonorous.
9. Oxides	Metals oxides are basic in nature.	Non-metallic oxides are acidic in nature.

II. CHEMICAL PROPERTIES OF METALS

(A) Reaction with Air :

Metals combine with oxygen to form metal oxide.

Metal + O₂ → Metal oxide

Example :

(i) 2Cu + O₂ → 2CuO
Copper oxide (black)
(ii) 4Al + 3O₂ → 2Al₂O₃
Aluminium oxide
(iii) 2Mg + O₂ → 2MgO

Different metals show different reactivites towards O₂.
• Na and K react so vigorously that they catch fire if kept in open so they are kept immersed in kerosene.
• Surface of Mg, Al, Zn, Pb are covered with a thin layer of oxide which prevent them from further oxidation.
• Fe does not burn on heating but iron fillings burn vigorously.
• Cu does not burn but is coated with black copper oxide.
• Au and Ag does not react with oxygen.

Amphoteric Oxides : Metals oxides which react with both acids as well as basesto produce salts and water are called amphoteric oxides.
Example :

Al₂O₃ + 6HCL → 2Alcl₃ + H₂O
Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O
Sodium Aluminate

(B) Reaction of Metals with Water :

Metal + Water → Metal oxide + Hydrogen
Metal oxide + Water → Metal hydroxide

Example :

(i) 2Na + 2H₂O → 2NaOH + H₂ + Heat
(ii) Ca + 2H₂O → Ca(OH)₂ + H₂
(iii) Mg + 2H₂O → Mg(OH)Al₂ + H₂
(iv) 2Al + 3H₂O → Al₂O₃ + 3H₂
(v) 3Fe + 4H₂O → Fe₃O₄ + 4H₂

(C) Reaction of Metals with Acids (Dilute) :

Metal + Dilute acid → Salt + H₂
Cu, Ag, Hg do not react with dilute acids.

Example :

(i) 2Fe + 6HCl → 2FeCl₂ + 3H₂
(ii) Mg + 2HCl → MgCl₂ + H₂
(iii) Zn + 2HCl → ZnCl₂ + H₂
(iv) 2Al + 6HCL → 2AlCl₃ + 3H₂

(D) Reaction of Metals with Solution of other Metal Salts :

Metal A + Salt solutin B → Salt solutin A + Metal B

• Reactive metals can displace less reactive metals from their compounds in solution form.

Fe + CuSo₄ → FeSO₄ + Cu

REACTIVITY SERIES

The reactivity series is list of metals arranged in the order of their decreasing acitivites.

k	Most reactive
Na Ca Mg Al
Zn	Reactivity decreases
Fe Pb H Cu Hg Ag
Au	Least reactive

Reaction of Metal with Non-metals :

• Reactivity of elements is the tendency to attain a completely filled valence shell.
• Atoms of the metals lose electorns from their valence shell to form cation.
• Atom of the non-metals gain electorns in the valence shell to form anion.

E.g., Formation of NaCl

Na → Na⁺ + e^-
2, 8, 1    2, 8
Sodium cation
Cl + e^- → Cl^-
2, 8, 7    2, 8, 8

Chloride anion

Ionic Compounds

The compounds formed by the transfer of electorns from a metal to a non-metal are called ionic compounds or electrovalent compounds.

Properties of Ionic Compounds :

1. Physical nature : The are solid and hard, generally brittle.
2. Melting and Boiling Point : They have high melting and boiling point.
3. Solubility : Generally soluble in water and insoluble in solvents such as kerosene, petrol etc.
4. Conduction of electricity : Ionic compounds conduct electricity in molten and solutin form but not in solid state.

Occurrence of Metals :

Minerals : The elements or compounds which occur naturally in the earth's crust are called minerals.
Ores : Minerals that contain very high percentage of particular metal and the metal can be profitably extracted from it, such minerals are called ores.

Extraction of Metals from Ores

Step 1. Enrichment of ores.
Step 2. Extraction of metals.
Step 3. Refining of metals.

Steps Involved in Extraction of Metals from Ores

Some Important Terms :

(a) Gangue : Ores are usually contaminated with large amount of impurities such as soil, sand etc. called gangue.
(b) Roasting : The sulphide ores are converted into oxides by heating strongly in the presence of excess air. The process is called roasting.

2ZnS + 3O₂ --Heat→ 2ZnO + 2SO₂

(c) Calcination : The carbonte ores are changed into oxides by heating strongly in limited air. This process is called calcination.

ZnCo₃ --Heat→ ZnO + CO₂

(d) Reduction : Metal oxides are reduced to corresponding metals by using reducing agent like carbon.

ZnO + C → Zn + CO

Refining of Metals :

The most widely used method for refining impure metal is electrolytic refining.
• Anode : Impure copper
• Cathode : Strip of pure copper
• Electrolyte : Solution of acidified copper sulphate.
(a) On passing the current thourgh electolyte, the impure metal from anode dissolve into the electolyte.
(b) An equivalent amount of pure metal from the electolyte is deposited at the cathode.
(c) The insolube impurities settle down at the bottom of the anode and is called andoe mud.

Corrosion :

The surface of some metals such as iron is corroded when they are exposed to moist air for a long period of time. This is called corrosion.
(i) Silver becomes black when exposed to air as it reacts with air to form a coating fof silver sulphide.
(ii) Copper reacts with moist carbon dioxide in the air and gains a green coat of copper carbonte.
(iii) Iron when exposed to moist air acquires a coating of a brown flaky substance called rust.

Prevention of Corrosion :

The rusing of iron can be prevented by painting, oiling, greasing, galvanizing, chrome plating, anodizing or making alloys.
Galvanization : It is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc.
Alloy : An alloy is a homogenous mixture of two or more metals or a metal and a non-metal.
Iron : Mixed with small amount of carbon becomes hard and strong.
Steel : Iron + Nickel and chromium.
Brass : Copper + Zinc
Solder : Lead + tin
Amalgn : If one of the metal is mercury (Hg).