Metals and Non-metals
Properties
| Property | Metals | Non-metals |
|---|---|---|
| Lustre | Shiny | Dull (iodine and graphite shine) |
| Hardness | Hard (sodium and potassium are soft) | Soft (diamond is hardest) |
| Malleability and ductility | Yes (gold and silver most) | Brittle |
| Conduction | Good conductors | Poor (graphite conducts) |
| Sonority | Yes | No |
| Melting point | Usually high (gallium, caesium melt in the hand) | Low |
| Oxides | Basic (some amphoteric) | Acidic |
| State | Solid (mercury liquid) | Solid, liquid (bromine), gas |
| Ions | Form cations | Form anions |
| Density | High (sodium, potassium, lithium float on water) | Low |
- Amphoteric oxides react with both acids and bases: Al2O3, ZnO.
- Malleable: can be beaten into sheets. Ductile: can be drawn into wires. Most malleable and ductile: gold. Best conductors: silver, then copper; lead is a poor conductor.
- Sodium and potassium are kept in kerosene (they catch fire in air). Phosphorus is stored under water.
Reactions of metals
- With oxygen: metal oxides (basic). Magnesium burns with a dazzling white flame. Aluminium forms a protective oxide layer.
- With water: sodium and potassium react violently; magnesium with hot water; iron with steam; copper, silver, gold do not react.
- With dilute acids: release hydrogen (except copper, silver, gold).
- Displacement: a more reactive metal replaces a less reactive one from its salt.
Reactivity series
Potassium > Sodium > Calcium > Magnesium > Aluminium > Zinc > Iron > Tin > Lead > (Hydrogen) > Copper > Mercury > Silver > Gold (most to least reactive).
Ionic compounds
- Formed by transfer of electrons from a metal to a non-metal (e.g. NaCl).
- Properties: solids, hard and brittle, high melting and boiling points, soluble in water, conduct electricity when molten or dissolved (not in the solid state).
Occurrence and extraction
- Mineral: a natural substance containing metals. Ore: a mineral from which the metal can be extracted profitably. Gangue is the earth impurity.
- Metallurgy is the whole process: concentration, extraction (reduction), refining.
| Metal reactivity | Method | Example |
|---|---|---|
| High (K, Na, Ca, Mg, Al) | Electrolysis of molten compound | Aluminium from bauxite (Al2O3), sodium from molten NaCl |
| Medium (Zn, Fe, Pb) | Roast / calcine then reduction with carbon | Zinc, iron |
| Low (Cu, Hg, Ag, Au) | Heating the ore | Cinnabar (HgS) gives mercury |
- Roasting: heating a sulphide ore in excess air. Calcination: heating a carbonate ore in limited air.
- Thermite reaction: aluminium reduces iron oxide, giving molten iron; used to weld rail tracks.
- Electrolytic refining gives pure copper (impure copper as anode, pure as cathode).
- Ores: bauxite (aluminium), haematite (iron), cinnabar (mercury), galena (lead), zinc blende (zinc), copper pyrites (copper), magnetite (iron), malachite (copper), rutile (titanium), pitchblende (uranium), monazite (thorium).
- Corrosion and alloys improve properties: brass (Cu + Zn), bronze (Cu + Sn), steel (Fe + C), stainless steel, duralumin (Al + Cu, light, aircraft), solder (Sn + Pb), German silver (Cu, Zn, Ni; no silver), amalgam (any alloy with mercury).
Non-metals
- Hydrogen, carbon, nitrogen, oxygen, sulphur, phosphorus, chlorine, iodine, bromine, fluorine and the noble gases.
- Allotropes of carbon: diamond (hardest, insulator), graphite (conducts electricity, slippery, used in pencils and lubricants), fullerene (C-60, buckminsterfullerene).
Keep practising
Notes are only half the work. Test yourself with questions and discuss doubts with other aspirants.
Prepared for exam revision from the NCERT Science textbooks for Classes 6 to 10 and standard sources. Space missions, awards and records change, so check official sources for recent facts. Found a mistake? Tell us.