Why is `FeI_(3)` not stable ?

Why is Cu^(+) ion not stable in aqueous solution ? or Why is Cu^(+) is not known in aqueous solution ?

Explain why Cu^+ ion is not stable in aqueous solution ?

Why H_(2) is more stable than H_(2)^(+) while He_(2)^(+) is more stable than He_(2) ?

While Fe^(3+) is stable Mn^(3+) is not stable in acitic solution because