Sodium
Sodium is a metal of group I, and it is highly reactive.
It is never found in nature as the metal. Because of that reactivity it exists only combined with other elements — and its principal compound, sodium chloride, is the main compound present in sea water.
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Activity 01 — with your teacher's help
- Observe and report how sodium metal is stored in the laboratory.
- Take a piece of sodium out with a pair of tongs, place it on a dry surface and cut it with a knife.
- Leave it exposed to the air for about five minutes, and note what you observe.
Because sodium is so reactive, it is stored under paraffin oil or kerosene, where air cannot reach it. A piece taken out of the oil shows no shine. It cuts very easily with a knife, and the cut surface has a silvery metallic lustre — which fades gradually within a short time.
Physical properties
- Soft enough to be cut with a knife.
- Less dense than water, so it floats on the surface — density 0.927 g cm−3.
- A conductor of electricity and heat.
Chemical properties
- Strongly reactive towards oxygen: it reacts rapidly with the oxygen of the air to form the oxide of the metal.
- Reacts rapidly with cold water to form sodium hydroxide and hydrogen gas.
- Reacts violently with dilute acids to form the salt of the metal and hydrogen gas — this reaction is very dangerous; do not attempt it.
Uses
- Producing sodium cyanide, needed for extracting gold and silver.
- Making sodium amalgam, used as a reducing agent in organic chemistry.
- Separating metals such as titanium and zirconium from their compounds.
- Producing dyes such as indigo, used to colour denim cloth.
- Electric lamps that give out yellow light.