Stability of Highest Oxidation State

[ritwik06]

1. The problem statement, all variables and given/known data

Why does the stability of highest oxiation state decreases from group 13 to group 17?

Ans: My book says, that with the increase in atomic number, difference in energies between ns and np orbitals increases. Is it right? If so then can u please explain what relation exists between the statements.

[GCT]

It's better to consider this in terms of electron affinity. The energies between ns and np orbitals increases because of the increase in effective nuclear charge i.e. " it wants the electrons more " .