Question
Draw the molecular orbital energy diagram for oxygen molecule (O2) and show that:
(i) It has a double bond
(ii) It has paramagnetic character.
Solution
Electronic structure of oxygen atom is 
Leaving out the 4 electrons in the 1s orbitals of two oxygen atoms constituting the molecule (represented as KK), the molecular orbital energy diagram for remaining 12 electrons of oxygen as molecule is shown:
(i) Electronic configuration:
(ii) Bond order: Here Nb = 8; Na = 4
The two oxygen atoms in a molecule of oxygen are united through two covalent bonds (i.e. a double bond).
(iii) Paramagnetic character : Since a molecule of oxygen has two unpaired electrons in the
orbitals, molecular oxygen should be paramagnetic.
Leaving out the 4 electrons in the 1s orbitals of two oxygen atoms constituting the molecule (represented as KK), the molecular orbital energy diagram for remaining 12 electrons of oxygen as molecule is shown:(i) Electronic configuration:
(ii) Bond order: Here Nb = 8; Na = 4
The two oxygen atoms in a molecule of oxygen are united through two covalent bonds (i.e. a double bond).
(iii) Paramagnetic character : Since a molecule of oxygen has two unpaired electrons in the
orbitals, molecular oxygen should be paramagnetic.
