The molecule electronic configuration of oxygen molecule is.

Explanation

Ordinary ` O_(2)` moleucle has the electronic configuration
`sigma_(1s)^(2) sigma_(1s)^(**2) sigma_(2s)^(2) sigma_(2p_(z))^(**2) .pi_(2P_(x))^(2)pi_(2P_(y))^(2)pi_(2P_(x))^(**1)pi_(2P_(y))^(**2)`
Multiplicity = (2S + 1 ) Where S = total electron spin
` = 2 ((1)/(2) + (1)/(2)) + 1 = 3 ` " "` [ S = (1)/(2) + (1)/(2) ` because two electons have parallel spins]
Hence , it is in the triplet state
if two electrons pair up ` S = (1)/(2) - (1)/(2) = 0 ` (because they will have opposite spin)
Spin multiplicity = `2S + 1 = 0 + 1 = 1 `
This is called singlet state . Hence, electronic configuration of `O_(2)` molecule in the single state will be
`sigma_(1s)^(2) sigma_(1s)^(**2) sigma_(2s)^(2) sigma_(2s)^(**2)sigma_(2p_(z))^(2) .pi_(2P_(x))^(2)pi_(2P_(y))^(2)pi_(2P_(x))^(**2)pi_(2P_(y))^(**0)`