What is Hund's rule? Why is it important when writing or­bital diagrams?

Solution 22Q

Here, we are going to state Hund’s rule and discuss why it is important when writing orbital diagrams.

Step 1:

According to Hund’s rule, electron pairing will not take place in orbitals of same energy(subshell) until each orbital is singly filled.

For example, there are three p- orbitals(px, py and pz) of the p - subshell in a principal energy level. According to Hund’s rule, each of the three p-orbitals must get one electron of parallel spin before any one of them receives the second electron of opposite spin.