Why are `Ni^(2+)` compounds thermodynamically more stable than `Pt^(2+)` compounds whereas `Pt^(4+)` compounds are relatively more stable than `Ni^(4+)` compounds ?

Explanation

As sum of 3rd and 4th I.E. of Ni is very high than that of 1st and 2nd IE of Ni so `Ni^(2+)` compounds are more stable, But in case of `Pt, IE_3+ IE_4 and IE_1 +IE_2` difference is very less. So `Pt^(+4)` is more stable. Moreover Ni(II) compounds are formed more easily than Pt(II) compounds. Also `IE_1 + IE_2+IE_3+IE_4` for Pt is less than that of Ni, Pt(IV) is formed more easily than Ni(IV) compounds.