Question

Why Ni (II) compounds are thermodynamically more stable than Pt (II) compounds

where as Pt (IV) compounds more stable than Ni (II) compounds ?

Answer 1

Since the ionization energy of Ni2+ is less thanthat for Pt2+, therefore Ni2+, compounds are thermodynamically more stable than Pt2+compounds. Pt4+ compounds are stable than Ni4+ compounds because the energy needed to remove 4 electrons in Pt is less than that in Ni.