Question

What is the correct name for the compound with the formula `CrPO_4`?

Answer 1

Chromium(III)phosphate

Explanation:

Since the oxidation states of `P` can be `+3or+5`, (and here it is obviously `+5`), and the oxidation state of `O` is `-2` the total charge of the phosphate will be `-3`, or `PO_4^(3-)`
It is called phosphate because of this higher state (otherwise it would be called phosphite and be `PO_3^(3+)`).
To compensate the chromium must have an oxidation state of `+3`, or `Cr^(3+)`, that's where the Lation `III` comes in (because `Cr` kan have many different oxidation numbers, up to `+7`).