Among ferrous and ferric ions, which one is more stable? Why? 

Explanation

Electronic configuration of `Fe(26): [Ar]4s^(2)3d^(6)` Ferrous ion `Fe^(2+) : [Ar] 4s^(0) 3d^(5)`, Ferricion `Fe^(3+): [Ar]4s^(0)3d^(5)`. Ferric ion is more stable than ferrous ion. This is because ferric ion has half filled d-subshell stable electronic configuration.