Q41 / 180 · KCET 2013 · Chemistry

Which of the following is diamagnetic?

  • A
    $\mathrm{H}_{2}^{+}$
  • B
    $\mathrm{He}_{2}^{+}$
  • C
    $\mathrm{O}_{2}$
  • Correct answer
    D
    $\mathrm{N}_{2}$

Solution

$\mathrm{MO}$ configuration of $\mathrm{H}_{2}^{+}: \sigma 1 s^{1}$ $\mathrm{MO}$ configuration of $\mathrm{He}_{2}^{+}: \sigma 1 s^{2}, \star^{*} s^{1}$ $\mathrm{MO}$ configuration of $\mathrm{N}_{2}$ : $\sigma 1 s^{2}$, ซั $1 s^{2}, \sigma 2 s^{2}, \stackrel{*}{\sigma} 2 s^{2}, \pi 2 p_{y}^{2}=\pi 2 p_{z}^{2}, \sigma 2 p_{x}^{2}$ $\mathrm{MO}$ configuration of $\mathrm{O}_{2}$ : $\sigma 1 s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2}, \sigma 2 p_{x}^{2}, \pi 2 p_{y}^{2}$ $=\pi 2 p_{z}^{2}, \pi 2 p_{y}^{1}=\pi_{\pi}^{*} 2 p_{z}^{1}$ Hence, $\mathrm{O}_{2}$ is paramagnetic as it possesses two unpaired electrons.

Hence, the correct answer is option: 'D'.

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