Question

Explain Hund’s Rule with an example.

Answer 1

Hund’s Rule : 

According to this rule electron pairing in orbitals starts only when all available empty orbitals of the same energy are singly occupied.

(1) Ex : 

1. The configuration of carbon atom (Z = 6) is 1s² 2s²2p² 

2. The first four electrons go into the 1s and 2s orbitals. 

3. The next two electrons go into 2p_x and 2p_y orbitals.

4. But, they do not pair in 2p_x orbital. 

(2) Ex :

1. In oxygen atom (₈O), distribution of electrons is given below.

2.

 

3. Here, pairing of electrons in 2p_x orbital takes place after, 2p_x , 2p_y and 2p_z orbitals are filled with a single electron.