question_answer

Which is not in accordance to Aufbau principle?

A)  

B)  

C)  

D)   

Correct Answer: C

Solution :

Key Idea 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 \[1{{s}^{2}},\,\,2s,\,\,2p,\,\,3s,\,\,3p,\,\,4s,\,\,3d,\,\,4p,\,\,5s,\] ... 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.