All elements can be broadly classified as metals, non-metals, or metalloids. This classification is based on their physical and chemical properties. Understanding these properties helps us use materials wisely in daily life and industry.
Physical Properties of Metals
- Lustre – Metals have a shiny appearance (e.g., gold, silver, copper).
- Hardness – Most metals are hard (iron, steel), though sodium and potassium are soft enough to cut with a knife.
- Malleability – Metals can be beaten into thin sheets (gold is the most malleable metal).
- Ductility – Metals can be drawn into thin wires (gold and copper are highly ductile).
- Conductivity – Metals are good conductors of heat and electricity.
- Sonority – Metals produce a ringing sound when struck (used in bells).
- Melting point – Generally high (except mercury, which is liquid at room temperature).
Physical Properties of Non-Metals
- Non-metals are generally dull (no lustre), brittle (not malleable), and poor conductors of heat and electricity.
- Exceptions: graphite (a form of carbon) conducts electricity; diamond is the hardest natural substance.
- Non-metals may be solid (sulphur, carbon), liquid (bromine), or gas (oxygen, nitrogen, hydrogen) at room temperature.
Chemical Properties of Metals
- Reaction with oxygen – Metals react with oxygen to form metal oxides, which are generally basic.
- 4Na + O2 → 2Na2O (sodium oxide — basic)
- 2Mg + O2 → 2MgO (magnesium oxide — basic)
- Reaction with water – Sodium and potassium react vigorously with cold water; iron reacts only with steam.
- 2Na + 2H2O → 2NaOH + H2
- Reaction with acids – Most metals react with dilute acids to produce a salt and hydrogen gas.
- Fe + H2SO4 → FeSO4 + H2
Chemical Properties of Non-Metals
- Non-metals react with oxygen to form non-metal oxides, which are generally acidic.
- C + O2 → CO2 (carbon dioxide — acidic)
- S + O2 → SO2 (sulphur dioxide — acidic)
- Non-metals generally do not react with water or dilute acids to produce hydrogen.
Uses of Metals and Non-Metals
- Iron/Steel – Construction, machinery, vehicles.
- Copper – Electrical wires, cookware.
- Gold/Silver – Jewellery, electronic contacts.
- Oxygen – Respiration, medical use.
- Carbon – Fuel (coal), pencil leads (graphite), cutting tools (diamond).
- Nitrogen – Fertilisers, preserving food.
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A piece of copper is beaten into a thin sheet for making utensils. This demonstrates malleability, a key physical property of metals.
When magnesium ribbon burns in air, it reacts with oxygen to form white magnesium oxide (MgO), a basic metal oxide. This shows metals form basic oxides.
A piece of sodium is dropped into water. It reacts vigorously, fizzing and moving rapidly, producing sodium hydroxide (NaOH) and hydrogen gas. This illustrates how reactive some metals are with water.
Sulphur burns in air to form sulphur dioxide (SO2), which dissolves in water to form sulphurous acid — an acidic solution. This illustrates that non-metals form acidic oxides.
Iron nails in dilute sulphuric acid (H2SO4) slowly dissolve, producing iron sulphate (FeSO4) and hydrogen gas (which can be tested with a lit matchstick — it burns with a pop sound).
Graphite, a non-metal (form of carbon), conducts electricity and is used in dry cell electrodes. This is an important exception to the general rule that non-metals are insulators.
Diamond, another form of carbon, is the hardest natural substance and is used for cutting glass and drilling rocks — showing the diverse properties that even a single element (carbon) can display.
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Key Distinctions
| Property | Metals | Non-Metals |
|----------|--------|------------|
| Lustre | Shiny | Dull (mostly) |
| Malleability | Yes | No (brittle) |
| Conductivity | Good | Poor (except graphite) |
| Oxide nature | Basic | Acidic |
| State at RT | Mostly solid | Solid, liquid, or gas |
Common mistakes
- Assuming all metals are solid: mercury is a liquid metal at room temperature.
- Assuming all non-metals are poor conductors: graphite is a notable exception.
- Confusing malleability (beaten into sheets) with ductility (drawn into wires).
Summary
Metals are typically shiny, malleable, ductile, sonorous, and good conductors. Non-metals lack these properties and are usually brittle and poor conductors. Metals form basic oxides; non-metals form acidic oxides. Exceptions like mercury (liquid metal) and graphite (conducting non-metal) make this topic rich and interesting.