The number of paramagnetic species among the following is ______. $\mathrm{B}_{2}, \mathrm{Li}_{2}, \mathrm{C}_{2}, \mathrm{C}_{2}^{-}, \mathrm{O}_{2}^{2-}, \mathrm{O}_{2}^{+}$ and $\mathrm{He}_{2}^{+}$

JEE Main · 2022 · 28 Jul 2022 · Shift 1 · Chemical Bonding and Molecular Structure

The number of paramagnetic species among the following is ______.

B_{2}, Li_{2}, C_{2}, C_{2}^{-}, O_{2}^{2 -}, O_{2}^{+}

and

He_{2}^{+}

Answer: 4

Using molecular orbital theory to determine unpaired electrons:

B_{2}

has 2 unpaired electrons (paramagnetic),

Li_{2}

has all paired (diamagnetic),

C_{2}

has all paired (diamagnetic),

C_{2}^{-}

has 1 unpaired electron (paramagnetic),

O_{2}^{2 -}

has all paired (diamagnetic),

O_{2}^{+}

has 1 unpaired electron (paramagnetic),

He_{2}^{+}

has 1 unpaired electron (paramagnetic). Total paramagnetic species = 4.

JEE Main · 2022 · 28 Jul 2022 · Shift 1 · Integer answer