Question

What is the formula for vanadium(V) phosphate?

Answer 1

`"V"_3("PO"_4)_5`

Explanation:

Vanadium(V) phosphate is an ionic compound made up of vanadium(V) cations and phosphate anions.

The (V) Roman numeral used to name the cation indicates that vanadium, a transition metal, is in its `+5` oxidation state, i.e. the vanadium cation carries a `5+` charge.

`"V"^(5+) ->` the vanadium(V) cation

The phosphate anion is a polyatomic ion that consists of `1` phosphorus atom and `4` oxygen atoms. This polyatomic ion carries a `3-` charge.

`"PO"_4^(3-) ->` the phophate anion

Now, vanadium(V) phosphate is a neutral compound, which means that the overall positive charge coming from the cations must be balanced by the overall negative charge coming from the anions.

In this case, you will need `3` vanadium(V) cations and `5` phosphate anions to balance out an overall `15+` charge coming from cations and `15-` coming from the anions.

`color(blue)(3)"V"^color(red)(5+) + color(red)(5)"PO"_ 4^color(blue)(3-) -> "V"_ color(blue)(3)("PO"_ 4)_color(red)(5)`

Therefore, the ionic formula for vanadium(V) phosphate will be

`"V"_3("PO"_4)_5 ->` vanadium(V) phosphate