Why are there only certain values of the number of unpaired electrons for a
given metal ion? For example, complexes of Fe(II) and Co(III) can only have
zero or 4 unpaired electrons, never two. Complexes of Fe(III) can only have 5
unpaired electrons or 1 unpaired electron.
Why is it that for Ni2+ complexes, all octahedral complexes have 2 unpaired
electrons (paramagnetic), but square planar complexes are diamagnetic (no
unpaired electrons)?
C