Cheatsheet

Physical Properties — Metals

• Lustrous — shiny surface when freshly cut
• Malleable — can be beaten into thin sheets (Au, Ag most malleable)
• Ductile — can be drawn into wires (Au most ductile — 2 km wire from 1 g)
• Good conductors of heat & electricity (Ag > Cu > Au > Al)
• Sonorous — produce ringing sound when struck
• Generally hard, high melting/boiling points
• Exceptions: Na, K — soft (cut with knife); Hg — liquid; Pb, Na — poor conductors

Physical Properties — Non-Metals

• Non-lustrous (exception: iodine, diamond)
• Brittle — break when hammered
• Non-ductile, cannot be drawn into wires
• Poor conductors (exception: graphite conducts electricity)
• Generally soft, low melting/boiling points
• Exist as solids, liquids, or gases at room temp (Br₂ = liquid)
• Low density compared to metals

Chemical Properties of Metals

Reactivity Series

Ionic Bonding

• Metals lose electrons → form cations (Na → Na⁺ + e⁻)
• Non-metals gain electrons → form anions (Cl + e⁻ → Cl⁻)
• Electrostatic attraction between ions = ionic bond
• Example: Na⁺Cl⁻ — transfer of 1e⁻ from Na to Cl

Properties of Ionic Compounds

• High melting & boiling points — strong electrostatic forces
• Hard but brittle — rigid lattice, layers crack on shifting
• Solid state: don't conduct electricity (ions fixed)
• Molten/Aqueous: conduct electricity (ions free to move)
• Soluble in water, insoluble in organic solvents (kerosene, petrol)

Extraction of Metals — Steps

• Step 1: Concentration — Remove gangue (hydraulic washing, magnetic separation, froth flotation)
• Step 2: Conversion to oxide — Roasting (sulphide ores in air) or Calcination (carbonate ores without air)
• Step 3: Reduction — Using carbon/CO for mid-reactive metals; Electrolysis for highly reactive metals
• Step 4: Refining — Electrolytic refining (anode = impure, cathode = pure, electrolyte = metal salt solution)

Roasting vs Calcination

Corrosion

• Corrosion = surface of metal attacked by air, moisture, acids, etc.
• Rusting of iron: Fe + O₂ + H₂O → Fe₂O₃·xH₂O (hydrated iron oxide)
• Needs BOTH O₂ and moisture; salt/acid accelerates it
• Silver tarnishing: reacts with H₂S in air → Ag₂S (black)
• Copper turning green: reacts with CO₂ + H₂O → CuCO₃·Cu(OH)₂

Prevention of Corrosion

• Painting / Oiling / Greasing — physical barrier
• Galvanisation — zinc coating (sacrificial protection)
• Electroplating — layer of Cr, Ni, Sn on surface
• Alloying — stainless steel (Fe + Cr + Ni + C)
• Anodising — thickening Al₂O₃ layer on aluminium

Important Alloys