Question

Which is not in accordance to aufbau principle?

• A.
• B.
• C.
• D.

Answer 1

Answer: (C)

Aufbau principle states that in the ground state of an atom, the orbital with lower energy is filled up first before the filling of the orbitals with a higher energy commences.
Increasing order of energy of various orbitals is
$1s,2s,2p,3s,3p,4s,3d,4p,5s,\dots$ etc.
Therefore,

is not obeyed by aufbau principle. Without fully filling of $s$ subshell electrons cannot enter in $p$ subshell in ground state of atom.