Metals and Non-Metals (RRB)

Metals (left side of periodic table) — about 80% of all elements.

Physical properties:

• Lustrous (shiny when freshly cut/polished).
• Good conductors of heat and electricity.
• Malleable (hammered into sheets — gold can be beaten to 0.0001 mm).
• Ductile (drawn into wires).
• High density (except sodium, potassium).
• High melting point (except mercury, gallium, caesium).
• Solid at room temperature (except mercury, gallium).
• Sonorous (ring when struck).

Chemical properties:

• React with oxygen → metal oxides (which are usually basic).
• React with water → metal hydroxide + H₂ (depends on reactivity).
• React with acids → salt + H₂.
• Form positive ions (cations) in reactions.

Non-metals (right side, including upper row) — fewer in number (~17).

Physical properties:

• Dull (not shiny — except iodine and graphite).
• Poor conductors of heat and electricity (except graphite).
• Brittle (break when hammered).
• Low density.
• Low melting/boiling points.
• Most are gases or solids at room temperature; bromine is the only liquid non-metal.
• Not sonorous.

Chemical properties:

• React with oxygen → non-metal oxides (acidic or neutral).
• Don't react with acids generally (don't displace H₂).
• Form negative ions (anions) in reactions.

Reactivity series (metals):
K > Na > Ca > Mg > Al > Zn > Fe > Sn > Pb > H > Cu > Hg > Ag > Au.

• Above H: displace H₂ from acids and water.
• Below H: don't displace H₂.
• A more reactive metal displaces a less reactive metal from its salt solution. Iron in CuSO₄ → FeSO₄ + Cu (red-brown deposit).

Metalloids: elements with intermediate properties — boron, silicon, germanium, arsenic, antimony, tellurium. Useful as semiconductors.

Alloys — mixtures of metals (and sometimes non-metals) to improve properties:

• Steel: Fe + C (0.2–2%). Stainless steel: + Cr + Ni.
• Brass: Cu + Zn (yellow, used in instruments).
• Bronze: Cu + Sn (used in bells, statues).
• Solder: Pb + Sn (low melting; electronics — being replaced by lead-free alloys).

Extraction of metals — depends on reactivity:

1. Most reactive metals (K, Na, Ca, Mg, Al): extracted by electrolysis of molten salts. Cannot be reduced chemically.
2. Moderately reactive (Zn, Fe, Pb): ores are roasted/calcined, then reduced with carbon. Example: ZnO + C → Zn + CO.
3. Least reactive (Cu, Ag, Au): found native (uncombined) or extracted by simple roasting.

Common ores and their metals:

• Bauxite (Al₂O₃·xH₂O) → aluminium.
• Haematite (Fe₂O₃) and Magnetite (Fe₃O₄) → iron.
• Galena (PbS) → lead.
• Pyrite (FeS₂) → iron.
• Cinnabar (HgS) → mercury.
• Calamine (ZnCO₃) → zinc.
• Copper pyrite (CuFeS₂) → copper.

Corrosion:

• Rusting of iron: Fe + O₂ + H₂O → hydrated Fe₂O₃ (red-brown). Requires both O₂ and water. Prevented by painting, galvanising (Zn coating), oiling, electroplating.
• Silver tarnish: Ag₂S (black) from sulphur in air.
• Copper patina: green CuCO₃·Cu(OH)₂ — protective layer (Statue of Liberty).

Aluminium uses: planes, foil, cans, kitchenware, electrical cables (high voltage transmission), window frames. Resists corrosion due to thin Al₂O₃ layer.

Iron uses: steel (buildings, vehicles, machines), wrought iron (decorative), cast iron (pipes).

Copper uses: electrical wires, plumbing, alloys (brass/bronze).

Sodium uses: street lamps, coolant in some nuclear reactors, Na vapour lamps (yellow).

Common RRB facts:

• Iron is the most-used metal in the world.
• Aluminium is the most abundant metal in Earth's crust (~8%).
• Mercury is the only metal liquid at room temperature (m.p. −39°C).
• Tungsten has the highest melting point of any metal (3422°C) — used in bulb filaments.
• Osmium is the densest natural element.
• Gold is the most malleable metal — 1 g can be drawn to 2.4 km of wire.
• Silver is the best conductor of electricity at room temperature.
• 24 carat gold is pure gold; 22 carat is 91.6% gold (others alloyed with Cu, Ag).

Diamond and graphite are both pure carbon but with very different properties due to crystal structure: diamond is tetrahedral 3D, graphite is layered 2D.