question_answer

Out of the following electronic arrangements for outer electronic configuration.

I.

II.

III.

IV.

The most stable arrangement is

A) Only I

B) Only II 

C) Only III

D) Only IV

Correct Answer: A

Solution :

Most stable arrangement is

Because, (I) according to Aufbau principle, electrons enter in the subshell of an atom in the increasing order of energy. (II) according to Hund's rule of maximum multiplicity, pairing of electrons in the orbitals of a subshell does not take place until all orbitals of a subshell are singly occupied.