Question

how to find no. of unpaired electrons for an element

Answer 1

First do the electronic configuration by aufbau principle as oxygen atom

1S2,2S2,2P4

Then draw the last orpitals using hund's rule ,

Put the elctrons in the orpitals in single form first then in pairs as,

2Px2,2Py1,2Pz1,, so, no of unpaird electrons in oxygen atom is 2e