question_answer

Presence of three unpaired electrons in p-orbital of phosphorus can be explained by

A)  Aufbau rule      

B)  Hund's rule

C)  Faults rule       

D) \[(n+7)\]rule

Correct Answer: B

Solution :

 According to Hund's rule, electron pairing will not take place in orbitals of same energy(same sub-shell) until each orbital is first singly filled with parallel spin. \[P(15)=1{{s}^{2}},2{{s}^{2}}2{{p}^{6}},3{{s}^{2}}3{{p}^{3}}\]