The two lines in a circle represents sodium, and is one of the element symbols developed by John Dalton in the 19th century. The orange glow is like the colour of sodium street lighting and the spiked ‘flash’ symbol reflects the element's high reactivity.

Fact Box

Uses

Sodium is used as a heat exchanger in some nuclear reactors, and as a reagent in the chemicals industry. But sodium salts have more uses than the metal itself.

The most common compound of sodium is sodium chloride (common salt). It is added to food and used to de-ice roads in winter. It is also used as a feedstock for the chemical industry.

Sodium carbonate (washing soda) is also a useful sodium salt. It is used as a water softener.

History

Salt (sodium chloride, NaCl) and soda (sodium carbonate, Na2CO3) had been known since prehistoric times, the former used as a flavouring and preservative, and the latter for glass manufacture. Salt came from seawater, while soda came from the Natron Valley in Egypt or from the ash of certain plants. Their composition was debated by early chemists and the solution finally came from the Royal Institution in London in October 1807 where Humphry Davy exposed caustic soda (sodium hydroxide, NaOH) to an electric current and obtained globules of sodium metal, just as he had previously done for potassium, although he needed to use a stronger current.