What is Phosphorus?
Diagram of a phosphorus atom
Phosphorus atoms have fifteen protons and sixteen neutrons, so they're just a little lighter than sulphur atoms, in the middle of the range for atoms. Stars make phosphorus when two oxygen atoms get very hot and squash together into one phosphorus atom.
On earth, nearly all of the phosphorus atoms have combined with oxygen atoms to make molecules of phosphate. People use phosphates mainly as fertilizers for plants, but also in matches, where the phosporus reacts with sulphur when you strike a match to make the flame. (Phosphorus itself is poisonous to people, so today matches use a different version of phosphorus that's safer.)
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