Atomic Structure

Anions which contain more than one element are called Compound Anions.

Below are common compounds which form anions (negatively charged ions).
NO₃^-,   CO₃^2-,   SO₄^2-,   PO₄^3-.
They are called
nitrate, carbonate, sulfate and phosphate.

In most chemical reactions that you will come across, compound anions do not
split up but stay as a single species carrying a charge.

For example the Nitrogen and Oxygen in Nitrate (NO₃)
usually stay together as if nitrate is just one thing - see an example.

Examples of ionic compounds with these compound anions are

LiNO₃, Mg(NO₃)₂,       lithium nitrate, magnesium nitrate,           
Na₂CO₃, CaCO₃,        sodium carbonate, calcium carbonate,     
K₂SO₄, MgSO₄,          potassium sulfate, magnesium sulfate,    
 K₃PO₄, Ca₃(PO₄)₂,     potassium phosphate, calcium phosphate.

The other common compound anion is hydroxide, (OH)^-.
See acids and alkalis.

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