Question

What is the correct formula of an ionic compound containing Fe-2 and PO4-3 and how is it called?

Answer 1

The ionic formula is `Fe_3` `(P`O4`)_2`

We can write the formula using charge balance method. Ferrous ion has +2 charge and the phosphate ion has -3 charge.

let us count the number of Ferrous Ions and Phosphate ions we need to have to balance the overall positive and negative charge.

if we have three ferrous ions, we will have total of 3 x (+2) = +6 charge. To have six units of negative charge, we need two phosphate ions because each phosphate ion has -3 charge, 2x (-3) = -6.

so the formula becomes , it is called Ferrous Phosphate or
Iron (II) Phosphate

`Fe_3` `(P`O4`)_2`