How many lone pairs of electrons are represented in the Lewis structure of a phosphate ion (PO43-) ? 10 12 21 24

To illustrate the Lewis structure,

P has 5 valence electrons

O has 6 valence electrons (each for 4 oxygen)

And finally, for every negative charge, there is an additional valence electron

We should add these all up = 5 + 24 + 3 = 32 valence electrons

With this, we can be guided to illustrate the lewis structure as P as central atom and the 3 oxygen each with a single bond with P and 1 oxygen with a double bond with P. We place the valence electrons until octet rule is satisfied,

we will be left with 12 lone pairs for phosphate ion.