Important Salts:

Common Salt ($NaCl$): Raw material for $NaOH, Na_2CO_3, NaHCO_3$.
Sodium Hydroxide ($NaOH$): Caustic soda, from Chlor-alkali process: $2NaCl(aq) + 2H_2O(l) \to 2NaOH(aq) + Cl_2(g) + H_2(g)$.
Bleaching Powder ($CaOCl_2$): From $Cl_2(g)$ and $Ca(OH)_2(s)$: $Ca(OH)_2 + Cl_2 \to CaOCl_2 + H_2O$. Used for bleaching, disinfectant.
Baking Soda ($NaHCO_3$): For baking, antacid. Decomposes on heating: $2NaHCO_3(s) \xrightarrow{heat} Na_2CO_3(s) + H_2O(l) + CO_2(g)$.
Washing Soda ($Na_2CO_3 \cdot 10H_2O$): For cleaning, glass, soap, paper industries.
Plaster of Paris ($CaSO_4 \cdot \frac{1}{2}H_2O$): From heating Gypsum: $CaSO_4 \cdot 2H_2O \xrightarrow{373K} CaSO_4 \cdot \frac{1}{2}H_2O + 1\frac{1}{2}H_2O$. Sets on mixing with water.

3. Metals and Non-metals

Metals: Lustrous, malleable, ductile, sonorous, good conductors of heat and electricity.
- Examples: $Fe, Cu, Al, Au, Ag$.
- Exceptions: Mercury (liquid), Sodium/Potassium (soft, low MP).
Non-metals: Dull, brittle, non-sonorous, poor conductors (insulators).
- Examples: $C, S, P, O_2, N_2, Cl_2$.
- Exceptions: Graphite (conductor), Iodine (lustrous).
Chemical Properties:
- Reaction with Oxygen:
  - Metals form basic oxides (e.g., $2Mg(s) + O_2(g) \to 2MgO(s)$).
  - Amphoteric oxides (react with both acids and bases): $Al_2O_3, ZnO$.
    - $Al_2O_3 + 6HCl \to 2AlCl_3 + 3H_2O$
    - $Al_2O_3 + 2NaOH \to 2NaAlO_2 + H_2O$
  - Non-metals form acidic oxides (e.g., $C(s) + O_2(g) \to CO_2(g)$).
- Reaction with Water:
  - Highly reactive metals (Na, K) react vigorously with cold water: $2Na(s) + 2H_2O(l) \to 2NaOH(aq) + H_2(g) + Heat$.
  - Mg reacts with hot water. Al, Fe, Zn react with steam: $3Fe(s) + 4H_2O(g) \to Fe_3O_4(s) + 4H_2(g)$.
- Reaction with Acids: Metals above Hydrogen in reactivity series react with dilute acids to produce $H_2$ gas.
  - $Zn(s) + 2HCl(aq) \to ZnCl_2(aq) + H_2(g)$.
- Reactivity Series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt (decreasing reactivity).
Ionic Bonds: Formed by transfer of electrons (metal + non-metal).
- Cations (positive ions) and Anions (negative ions) attract.
- Example: $Na \to Na^+ + e^-$, $Cl + e^- \to Cl^-$. $Na^+ + Cl^- \to NaCl$.
- Properties: High MP/BP, soluble in water, conduct electricity in molten/aqueous state.
Metallurgy: Extraction of metals from ores.
- Enrichment of Ores: Removing gangue (impurities).
- Extraction:
  - Highly reactive (K, Na, Ca, Mg, Al): Electrolytic reduction. E.g., Electrolysis of molten $NaCl \to Na + Cl_2$.
  - Medium reactive (Zn, Fe, Pb, Cu):
    - Calcination (for carbonate ores): $ZnCO_3(s) \xrightarrow{heat} ZnO(s) + CO_2(g)$.
    - Roasting (for sulphide ores): $2ZnS(s) + 3O_2(g) \xrightarrow{heat} 2ZnO(s) + 2SO_2(g)$.
    - Reduction: $ZnO(s) + C(s) \to Zn(s) + CO(g)$.
  - Low reactive (H