Chemistry - GENERAL CHEMISTRY Question with Solution | TestHub

Ca (Z = 20):

$[Ar]4s^2$

Valence shell electrons = 2, penultimate shell electrons = 8.

Ar (Z = 18):

$1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Valence shell electrons = 8, penultimate shell electrons = 8.

V³⁺ (Z = 23):

$V=[Ar]3d^{3}4s^2$, $V^{3+}=[Ar]3d^2$

Valence shell electrons $\ne$ penultimate shell electrons.

Fe³⁺ (Z = 26):

$F{e}^{3+}=[Ar]3d^5$

Valence shell electrons $\ne$ penultimate shell electrons.

Therefore, the correct answer is:

(B) Ar