Which is more stable Fe2+ or Fe3+?

[Kahizinn]

I understand that Iron3+ has a half filled 3-d level, but I also know that in reality when one electron is lost from elemental iron, the lone pair from the 3-d level will move to the 4s level to stablelize it.

What I really want to know is which ion is more abundant in nature?

Thanks guys

 

[Borek]

It depends on how you define "nature". In oxygen rich atmosphere iron easily gets oxidized to +3, in early times of Earth atmosphere didn't contain free oxygen, so iron was usually found as +2.