Determining Valence e-

[Jeffrey Doeve 2I]

I was wondering how to determine the number of valence electrons in a transition metal. I thought the definition of valence e- were the electrons in the outermost shell of an atom. Using electron configuration for Mn4+, it indicates that it has 3 valence e-([Ar]3d3). However, going off the valence e- definition, it would technically 11 valence e- because there are 11 e- in the 3rd and outermost shell. Thanks in advance!

[Isabella Chou 1A]

I'm not quite entirely sure either, but here is what I think. For Mn for example, since its electron configuration is [Ar] 3d5 4s2, I would think Mn has 7 valence electrons (5 in the 3d subshell and 2 in the 4s subshell). When Mn becomes Mn 4+, it thus loses 4 valence electrons, 2 electrons from the 4s subshell and 2 electrons from the 3d subshell. Then, Mn 4+ ends up with 3 valence electrons remaining.

[Benjamin Chen 1H]

To add, I think neutral Transition Metals in row 4 have 2 valence electrons since the outer most shell is 4s2 (unless they are special cases like Cr and Cu who would have 1 probably). But transition metals are unique since they don't have a filled inner shell (ie the d-orbital electrons).

[Alex Mele 2A]

I think you determine this based on electron configuration. Mn normally has 7 valence electrons ([Ar]4s²3d⁵) so Mn4+ has only 3. The reason both 4s and 3d electrons can act as valence electrons is because these orbitals have a small energy difference.