Metals & Non-Metals - Class Notes | Vardaan Learning Institute

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1. Physical Properties & Key Exceptions

Elements are divided into Metals and Non-Metals based on physical and chemical behavior. Here is the concise comparison and high-yield board exceptions:

Board High-Yield: Physical Exceptions

Property	General Rule	Exceptions to Remember
State	Metals are solids, non-metals solids/gases	Mercury ($Hg$) is a liquid metal. Bromine ($Br_2$) is a liquid non-metal.
Hardness	Metals are hard	Alkali Metals ($Li, Na, K$) are so soft they can be cut with a knife.
Lustre	Non-metals lack lustre	Iodine ($I_2$) is a lustrous non-metal.
Melting Point	Metals have high MP	Gallium ($Ga$) & Caesium ($Cs$) have extremely low MP (melt on palm).
Allotropy	Non-metals have lower density/hardness	Diamond (Carbon) is the hardest natural substance. Graphite conducts electricity.

Thermal & Electrical Conductivity

Best Conductors of Heat: Silver ($Ag$) and Copper ($Cu$).
Poor Conductors of Heat: Lead ($Pb$) and Mercury ($Hg$).
Electrical Wires Coating: Wires are coated with PVC (Polyvinylchloride) or rubber because they are electrical insulators.
Sonorous: Metals produce a ringing sound when struck (used in school bells).

2. Chemical Properties of Metals

A. Reaction with Oxygen (Air)

Metal + Oxygen $\rightarrow$ Metal Oxide (Basic / Amphoteric)

Examples: $2Cu + O_2 \rightarrow 2CuO$ (Black Copper(II) Oxide), $4Al + 3O_2 \rightarrow 2Al_2O_3$.

Exam Favorite: Amphoteric Oxides

Oxides that react with both acids and bases to yield salt and water are Amphoteric Oxides ($Al_2O_3, ZnO$).

Aluminium Oxide Reactions:

Acidic reaction: $Al_2O_3 + 6HCl \rightarrow 2AlCl_3 + 3H_2O$
Basic reaction: $Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 \text{ (Sodium Aluminate)} + H_2O$

Zinc Oxide Reactions:

Acidic reaction: $ZnO + 2HCl \rightarrow ZnCl_2 + H_2O$
Basic reaction: $ZnO + 2NaOH \rightarrow Na_2ZnO_2 \text{ (Sodium Zincate)} + H_2O$

Key Process: Anodising

Anodising forms a thick protective layer of aluminium oxide on Al articles via electrolysis with dilute $H_2SO_4$ (Al as anode). This layer prevents further corrosion and accepts vibrant dyes.

B. Reaction with Water

Metal + Water $\rightarrow$ Metal Hydroxide / Oxide + Hydrogen Gas

Water Reaction Spectrum

Cold Water (Violent/Exothermic): $Na, K$ react violently; $H_2$ catches fire instantly. $Ca$ reacts less violently and floats ($H_2$ bubbles stick).
Hot Water: $Mg$ reacts with hot water to form $Mg(OH)_2$ and floats due to attached $H_2$ bubbles.
Steam Only: $Al, Fe, Zn$ react only with steam to form oxides (not hydroxides):
$2Al(s) + 3H_2O(g) \rightarrow Al_2O_3(s) + 3H_2(g)$
$3Fe(s) + 4H_2O(g) \rightarrow Fe_3O_4(s) + 4H_2(g)$
No Reaction: $Pb, Cu, Ag, Au$ do not react with water or steam at all.

C. Reaction with Acids & Aqua Regia

Metal + Dilute Acid $\rightarrow$ Salt + $H_2$.

$HNO_3$ Exception & Aqua Regia

Why $H_2$ is NOT evolved with $HNO_3$: $HNO_3$ is a strong oxidizing agent that oxidizes formed $H_2$ to $H_2O$ and gets reduced to $N_2O, NO,$ or $NO_2$.

Exception: $Mg$ and $Mn$ react with very dilute $HNO_3$ to evolve $H_2$ gas.

Aqua Regia: Fresh mixture of 3 parts conc. $HCl$ : 1 part conc. $HNO_3$. Highly corrosive liquid that dissolves gold ($Au$) and platinum ($Pt$).

3. Reactivity Series & Ionic Bonding

The Reactivity Series

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

(Decreasing Reactivity $\rightarrow$ Potassium is most reactive, Gold is least reactive)

Ionic Bonding (Electrovalent Bond)

Metals lose electrons to form cations ($Na^+$, $Mg^{2+}$) while non-metals gain electrons to form anions ($Cl^-$, $O^{2-}$), achieving stable octet noble gas configurations.

Properties of Ionic Compounds

Physical State: Hard and brittle crystalline solids (strong electrostatic force of attraction).
High MP & BP: Large energy needed to break strong inter-ionic forces ($NaCl$ MP = 1074 K).
Solubility: Soluble in polar solvents (water), insoluble in organic solvents (kerosene, petrol).
Electrical Conduction: Do not conduct in solid state (fixed ions), but conduct in molten or aqueous solution state (free moving ions).

4. Metallurgy: Extraction of Metals

Mineral: Naturally occurring element/compound in Earth's crust.
Ore: Mineral from which metal can be extracted profitably.
Gangue: Soil, sand, and earthy impurities associated with ore.

Extraction Methods Summary

Reactivity Level	Ores / Type	Extraction Process & Key Equations
Low Reactivity ($Hg, Cu$)	Sulphides ($HgS, Cu_2S$)	Roasting alone: $2HgS + 3O_2 \xrightarrow{\Delta} 2HgO + 2SO_2$ $2HgO \xrightarrow{\Delta} 2Hg + O_2$
Medium Reactivity ($Zn, Fe, Pb$)	Sulphides ($ZnS$) or Carbonates ($ZnCO_3$)	Roasting (Excess $O_2$): $2ZnS + 3O_2 \xrightarrow{\Delta} 2ZnO + 2SO_2$ Calcination (Limited $O_2$): $ZnCO_3 \xrightarrow{\Delta} ZnO + CO_2$ Reduction (with Carbon): $ZnO + C \rightarrow Zn + CO$
High Reactivity ($Na, Ca, Mg, Al$)	Molten Chlorides / Oxides	Electrolytic Reduction: At Cathode (-): $Na^+ + e^- \rightarrow Na$ At Anode (+): $2Cl^- \rightarrow Cl_2 + 2e^-$

Board Essential: Thermit Reaction

Reduction of iron oxide with Aluminium powder generates extreme heat, producing molten iron:

$$Fe_2O_3(s) + 2Al(s) \rightarrow 2Fe(l) + Al_2O_3(s) + \text{Heat}$$

Application: Used on-site to weld cracked railway tracks or heavy machinery parts.

Electrolytic Refining of Copper

Anode (+): Block of impure copper metal.
Cathode (-): Thin sheet of pure copper metal.
Electrolyte: Acidified $CuSO_4$ solution.
Anode Mud: Insoluble impurities that settle at the bottom below the anode.

5. Corrosion and its Prevention

Conditions for Rusting

Rusting of iron requires both Air ($O_2$) and Moisture ($H_2O$) simultaneously.

Corrosion Cases & Alloys

Silver: Turns black due to formation of Silver Sulphide ($Ag_2S$) with $H_2S$ in air.
Copper: Forms a green coating of Basic Copper Carbonate ($CuCO_3 \cdot Cu(OH)_2$) in moist $CO_2$.
Galvanisation: Coating steel/iron with a thin protective layer of Zinc ($Zn$). Zinc protects even if scratched (sacrificial protection).
Alloys (Homogeneous Mixtures):
- Brass: $Cu + Zn$ (lower conductivity than pure Cu)
- Bronze: $Cu + Sn$ (poor conductor of electricity)
- Solder: $Pb + Sn$ (low melting point for joining electrical wires)
- Stainless Steel: $Fe + Ni + Cr$ (hard, rust-free)
- Amalgam: Any alloy containing Mercury ($Hg$)
- 22-Carat Gold: 22 parts pure Gold + 2 parts Copper/Silver for strength

Class Notes • Metals & Non-Metals