Question

Consider the species (O2)2- and (O2)2+. According to molecular orbital theory, which of these species will be diamagnetic?

		(O2)2+ and (O2)2-
		(O2)2+
		(O2)2-
		neither is diamagnetic
		The magnetic property can only be determined for molecules, not ions.

Answer 1

1) for O22+

σ and σ* orbital can have maximum of 2 electrons

π and π* orbital can have maximum of 4 electrons

1 O atom have 8 electrons

Here, number of O is 2

so, total number of electrons in O2 is 16

Since charge is +2

Total number of electron = 14

So, total number of electrons to fill is 14

order of filling of orbitals is:

σ1s σ*1s σ2s σ*2s π2p σ2p π*2p σ*2p

Lets fill the orbital

the filled orbital is σ1s2 σ*1s2 σ2s2 σ*2s2 π2p4 σ2p2

The orbital σ2p2 has unpaired number of electrons

So, it is diamagnetic in nature

2) FOR O2-2

σ and σ* orbital can have maximum of 2 electrons

π and π* orbital can have maximum of 4 electrons

1 O atom have 8 electrons

Here, number of O is 2

so, total number of electrons in O2 is 16

Since charge is -2

Total number of electron = 18

So, total number of electrons to fill is 18

order of filling of orbitals is:

σ1s σ*1s σ2s σ*2s σ2p π2p π*2p σ*2p

Lets fill the orbital

the filled orbital is σ1s2 σ*1s2 σ2s2 σ*2s2 σ2p2 π2p4 π*2p4

The orbital π*2p4 has unpaired number of electrons

So, it is diamagnetic in nature

Answer: both are diamagnetic (option 1)