MCQ
If Hund's Rule does not hold good, then which of the following pairs is diamagnetic
  • A
    $B_2, O_2^+$
  • $C_2, O_2$
  • C
    $O_2^-, N_2$
  • D
    $N_2, NO$

Answer

Correct option: B.
$C_2, O_2$
b
$B_2 \rightarrow$ Total $e^- \Rightarrow 10$

$\sigma s^2 \sigma^* 1 s^2 \sigma_2 s^2 \sigma^*2 s^2 \pi 2 P_x^2=\pi 2 P_y{ }^0$.

diamagnetic

$O _2 \rightarrow$ Total $e^- \rightarrow 16$

$\sigma 1s^2 \sigma^*1 s^2 \quad \sigma 2 s^2 \quad \sigma^*2 s^2 \sigma 2 P_z^2 \,\,\pi 2 P_x^2=\pi 2 P_y^2\, \pi^*2 P_{x^2}=\pi 2 P_y{ }^0 \quad$ diagmagnetic

$N _2 \rightarrow$ diamagnetic.

$C _2 \rightarrow$ Total $e^- \Rightarrow 12$

$\sigma 1s^2 \sigma^*1s^2 \sigma 2 s^2 \sigma^*2 s^2 \pi 2 P_x^2=\pi 2 P_y 2$

diamagnetic

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