Why do IIIA-VIIIA elements not include d subshell as part of valence electrons?

[dolimitless]

For example, I understand that Selenium has six valence electrons, but why doesn't it include the 3d electrons as part of its # of valence electrons?

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[nze82]

For example, I understand that Selenium has six valence electrons, but why doesn't it include the 3d electrons as part of its # of valence electrons?

They actually do include the 3d sub-shell as part of their electron configuration.
In your example, the electron configuration of Se looks like:
[Ar], 4s2, 3d10, 4p4

 

[navneetdh]

They actually do include the 3d sub-shell as part of their electron configuration.
In your example, the electron configuration of Se looks like:
[Ar], 4s2, 3d10, 4p6

The reason why you only count the electrons in 4p as valence electrons, is that 4p is the sub-shell that is located farthest from the nucleus, and by definition, the electrons in this sub-shell are identified as valence electrons.

I am confused about the electronic configuration you gave for Se. Shouldnt Se be [Ar] 4s2 3d10 and 4p4

And the valence electrons include everything in 4th orbital
which is 4+2 Hence 6 Valence electrons.

D orbital electrons are not in the valence electrons because its 3rd orbital. And the rule is to count only the outermost orbital.

 

[nze82]

I am confused about the electronic configuration you gave for Se. Shouldnt Se be [Ar] 4s2 3d10 and 4p4

And the valence electrons include everything in 4th orbital
which is 4+2 Hence 6 Valence electrons.

D orbital electrons are not in the valence electrons because its 3rd orbital. And the rule is to count only the outermost orbital.

Yea! you're right! That was a typo. I put 4p6 instead of 4p4. Tnx for catching that.
And yes! you're right about the # of valence electrons. I'm not sure what I was smoking while posting the previous post.