Question

What is the name of `Ni_3(PO_4)_2`?

Answer 1

Nickel (II) phosphate or simply nickel phosphate.

Explanation:

If we have `Ni_3(PO_4)_2` we know that it means it's build of two parts:

`3Ni^(+2) + 2PO_4^(-3) rarr Ni_3(PO_4)_2`

We know the anion - that is, the negatively charged species - is phosphate, and we know the name and the charge of the metal.

IUPAC rules say nomenclature of simple salts with cationic metals (salts with only one cation and one anion) goes like

`M\e\t\al` `(char\g\e` `of` `m\e\t\al)` `anion`

So the name is

`Nickel` `(II)` `phosph\ate`

If you're more savvy with chemistry, you know that most of the time you'll be working with nickel, it'll only be in that charge. While there are compounds with `Ni^+` and `Ni^(+3)` or `Ni^(+4)` they're very rare, so rare that it isn't considered wrong to say the salt is just

`Nickel` `phosph\ate`

(Note that you can't do that with salts that have metals like Iron or Mercury, which commonly appear in more than one charge)