Answer:
The 2 in the formula means that, there are 2 phosphate anions that forms the salt.
Explanation:
Magnesium phosphate is a ionic salt.
The formula indicates that 3 moles of Mg and 2 moles of anion phosphate are contained in 1 mol of compound.
3Mg²⁺ + 2PO₄⁻³ → Mg₃(PO₄)₂
The phosphate anion comes from phosphoric acid and it is generated when the acid loses the 3 protons.
H₃PO₄ → 3H⁺ + PO₄⁻³
Phosphate has a negative charge of -3, so when it bond to magnesium, which has a charge of +2, there must be 3 magnesium and 2 phosphate to make a global charge +6 -6 in the ions
