Valence Electron Configuration

[Aya Watson 2B]

1E.25:

Give the notation for the valence-shell configuration (including the outermost d-electrons) of the group 15 elements.

The answer is ns^2 np^3, but I don't understand why it wouldn't be (n-1)d^3 ns^2 np^3

[Reza Hemmati 3L]

Hi!

I'm pretty sure that you only count the electrons in the highest energy level as valence. So, with group 15 the d sublevels would never be valence because the energy level of the d sublevel is 1 lower than the outermost s and p levels. This results in group 15 elements always having 5 valence electrons(2 from an s sublevel, 3 from a p sublevel).

Hope this helps! ^^