Sodium is a silvery-white metal, soft enough to be cut by a knife! The silvery shine of the freshly cut surface will soon become dulled as it reacts with air though – in fact sodium reacts with lots of things. Small pieces dropped in water will react violently, bouncing along the surface, while large chunks will simply explode!
The best place to go if you’re looking for sodium is the sea. Sodium ions are very soluble in water and so quickly get washed away from land into the oceans. Chloride ions are also abundant in the sea, so when you evaporate off sea water you are left with sodium ions and chloride ions joined together in crystals of sodium chloride (NaCl). These crystals are common table salt!
Sodium is one of the elements that animal life needs to survive. It is particularly important in allowing our nerves to work properly, and without our nerves we wouldn’t be able to feel anything or to move around. Because there’s not much salt available on land, we’ve evolved to find it delicious. Salt used to be considered so valuable that in Roman times soldiers were said to have been paid part of their wages in salt, which is where we get the word ‘salary’. Too much salt is actually very bad for you, but our bodies don’t realise this and tend to eat far too much of it in our everyday diet.
In medieval times another sodium compound, soda (sodium carbonate) was used as a headache remedy. Today sodium carbonate is used as a food additive (for example in ramen noodles), as a water softener, to counteract acidic chlorine in swimming pools, in taxidermy to boil away flesh from skull and bones, and in the making of glass. Sodium carbonate is also one of the main ingredients of sherbet powder. When it reacts with citric acid on your tongue, the reaction releases little bubbles of carbon dioxide which is what you feel as a cold fizzy sensation!