Metals and Non Metals Short Notes - Class 10 Science Chapter 3

Metals and Non-metals – Complete Notes

These notes cover classification of elements, physical and chemical properties, ionic compounds, metallurgy, corrosion and alloys in simple exam-oriented language.

1. Classification of Elements

• Total Elements: 118 known elements.
• Metals: 93 elements, placed on the left and centre of the periodic table.
• Non-metals: 18 elements, placed on the right side. Hydrogen is a non-metal but placed on the left.
• Metalloids: 7 elements like Boron, Silicon and Germanium show properties of both metals and non-metals.

Physical States

Most metals are solids. Mercury is the only liquid metal at room temperature.

Non-metals include 6 solids, 11 gases and 1 liquid, Bromine.

2. Comparison of Physical Properties

• Lustre: Metals are shiny. Non-metals are dull, except iodine and graphite.
• Hardness: Metals are generally hard, except sodium and potassium. Non-metals are soft, except diamond.
• Malleability and Ductility: Metals can be beaten into sheets and drawn into wires. Gold and silver are the best examples.
• Conductivity: Metals are good conductors. Silver is the best conductor. Lead and mercury are poor conductors. Graphite is a conducting non-metal.
• Sonority: Metals produce ringing sound when struck. Non-metals are not sonorous.

3. Chemical Properties of Metals

A. Ion Formation

Metals lose electrons and form positive ions called cations. This property is called electropositive nature.

Na → Na⁺ + e⁻

Mg → Mg²⁺ + 2e⁻

Al → Al³⁺ + 3e⁻

B. Reaction with Oxygen

Metals react with oxygen to form basic oxides.

4Na(s) + O₂(g) → 2Na₂O(s)

2Mg(s) + O₂(g) → 2MgO(s)

3Fe(s) + 2O₂(g) → Fe₃O₄(s)

2Cu(s) + O₂(g) → 2CuO(s)

Amphoteric Oxides

Oxides that react with both acids and bases are called amphoteric oxides. Examples are ZnO and Al₂O₃.

Al₂O₃(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂O(l)

Al₂O₃(s) + 2NaOH(aq) → 2NaAlO₂(aq) + H₂O(l)

ZnO(s) + 2NaOH(aq) → Na₂ZnO₂(aq) + H₂O(l)

C. Reaction with Water

• Sodium and potassium react violently with cold water and catch fire.
• Calcium reacts less violently and floats due to hydrogen bubbles.
• Magnesium reacts only with hot or boiling water.
• Iron, aluminium and zinc react only with steam.

2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + Heat

Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)

Mg(s) + 2H₂O(l) → Mg(OH)₂(aq) + H₂(g)

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

Zn(s) + H₂O(g) → ZnO(s) + H₂(g)

D. Reaction with Acids

Metal reacts with dilute acid to form metal salt and hydrogen gas.

Metal + Dilute Acid → Metal Salt + Hydrogen Gas

2Na(s) + 2HCl(aq) → 2NaCl(aq) + H₂(g)

Fe(s) + H₂SO₄(aq) → FeSO₄(aq) + H₂(g)

Nitric Acid Exception

Nitric acid usually does not give hydrogen gas because HNO₃ is a strong oxidising agent. It converts hydrogen into water. Only magnesium and manganese give hydrogen with very dilute nitric acid.

Mg(s) + 2HNO₃(aq) → Mg(NO₃)₂(aq) + H₂(g)

E. Reactivity Series and Displacement

A more reactive metal displaces a less reactive metal from its salt solution.

Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s)

K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt

4. Ionic Compounds

Ionic compounds are formed by transfer of electrons from metal atoms to non-metal atoms.

Na⁺ + Cl⁻ → NaCl

• They are generally hard solids.
• They have high melting and boiling points.
• They are usually soluble in water.
• They conduct electricity in molten or aqueous state.
• They do not conduct electricity in solid state.

5. Metallurgy: Extraction of Metals

Step 1: Concentration of Ore

Concentration of ore means removal of gangue, such as sand and soil.

Hydraulic Washing Froth Floatation Magnetic Separation

• Hydraulic Washing: Used for heavy oxide ores.
• Froth Floatation: Used for sulphide ores with pine oil.
• Magnetic Separation: Used for magnetic ores like haematite.

Step 2: Conversion to Oxide

Calcination

Heating carbonate ores in limited air is called calcination.

ZnCO₃(s) → ZnO(s) + CO₂(g)

Roasting

Heating sulphide ores in excess air is called roasting.

2ZnS(s) + 3O₂(g) → 2ZnO(s) + 2SO₂(g)

Step 3: Reduction to Metal

• Low reactivity metals: Obtained by heating alone.
• Medium reactivity metals: Reduced using carbon or aluminium.
• High reactivity metals: Extracted by electrolysis of molten salts.

2HgO(s) → 2Hg(l) + O₂(g)

ZnO(s) + C(s) → Zn(s) + CO(g)

Fe₂O₃ + 2Al → 2Fe(l) + Al₂O₃ + Heat

Cathode: Al³⁺ + 3e⁻ → Al

Step 4: Refining

Electrolytic refining is used to obtain pure metal. Impure metal is made anode and pure metal is made cathode. Impurities settle down as anode mud.

6. Corrosion and Alloys

Corrosion

Corrosion is the gradual deterioration of metals by the action of air, moisture or chemicals.

• Iron rust: Fe₂O₃.xH₂O
• Copper green coating: CuCO₃.Cu(OH)₂
• Silver black coating: Ag₂S

Aqua Regia

Aqua regia is a 3:1 mixture of concentrated HCl and concentrated HNO₃. It can dissolve gold.

Alloys

Alloys are homogeneous mixtures of metals or metals with non-metals. They are made to improve properties.

• Brass: Cu + Zn
• Bronze: Cu + Sn
• Solder: Pb + Sn
• Stainless Steel: Fe + Cr + Ni + C
• Amalgam: Any alloy containing mercury