Which of the following electronic configuration is not possible according to Hund's rule?

Options

A. `1s^(2)2s^(2)`
B. `1s^(2)2s^(1)`
C. `1s^(2)2s^(2)2p_(x)^(1)2p_(y)^(1)2p_(z)^(1)`
D. `1s^(2)2s^(2)2p_(x)^(2)`

Answer

D

Explanation

Configuration `1s^(2)2s^(2)2p_(x)^(2)` is not possible according to Hund's rule because the pairing of electrons in the orbitals belonging to the same subshell `(p, d`, or `f`) does not take place unital each orbital belonging to that subshell has got one electron each, `i.e., it is singly occupied.