Ion electron config

[linkin06]

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what is electronic config of iron (III) ion?

i was between [Ar]4s1 3d4
and [Ar]3d5

i chose [Ar]4s1 3d4 thinking it's good to have unpaired electrons and that you'd want to take electrons from 3d first, since it's a higher orbital by the "n+l" rule

kaplan says tho: The first two electrons are stripped from the outermost orbital, the s orbital

 

[sv3]

those not in periods I and II like having half filled shells. So it would "promote" a S electron to D in order to be half filled. If you remember this rule, it will also explain what happens if a transition metal were to lose an electron - it would do so in a way that allow it to have a half filled valenece shell where possible.

 

[linkin06]

but doesn't [Ar]4s1 3d4 have the same # of half filled orbitals

 

[sv3]

i meant in the outermost subshell
the transition metals like having 5 electrons in their D orbital, or obviously 10 to have a full shell. so you would s1d10 as opposed to s2d9.

i am not sure exactly why they act this way (although I have an idea) but this general rule has worked for me every time i've gotten a question like this.