Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYEasy

Which one of the following molecules is paramagnetic?

H $_2$

Li $_2$

C $_2$

O $_2$

Definition: According to Molecular Orbital Theory, a molecule is paramagnetic if it contains unpaired electrons in its molecular orbitals .
Analyze H $_2$ : Configuration is $\sigma_{1s}^2$ . All electrons are paired. It is diamagnetic .
Analyze Li $_2$ : Configuration involves filled $\sigma_{1s}, \sigma^*_{1s}, \sigma_{2s}$ orbitals. All electrons are paired. It is diamagnetic .
Analyze C $_2$ : Configuration ends with $\pi_{2p_x}^2 \pi_{2p_y}^2$ . All electrons are paired. It is diamagnetic .
Analyze O $_2$ : The electronic configuration is $\sigma_{1s}^2 \sigma^*_{1s}^2 \sigma_{2s}^2 \sigma^*_{2s}^2 \sigma_{2p_z}^2 (\pi_{2p_x}^2 = \pi_{2p_y}^2) (\pi^*_{2p_x}^1 = \pi^*_{2p_y}^1)$ . It contains two unpaired electrons in the antibonding $\pi^*$ orbitals. Therefore, O $_2$ is paramagnetic .

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