Mg3II(PVO4)2 + 2 H20 3 Mg0 + 2 H2IPVIO4

This is an oxidation-reduction (redox) reaction:

2 PV - 2 e- 2 PVI (oxidation)

4 H0 - 4 e- 4 HI (oxidation)

3 MgII + 6 e- 3 Mg0 (reduction)

Change the oxidation states