MCQ
Among the following molecules / ions $C_2^{2-} ,N_2^{2-} ,O_2^{2-},O_2$ which one is diamagnetic and has the shortest bond length ?
- A$O_2^{2-}$
- ✓$C_2^{2-}$
- C$O_2$
- D$N_2^{2-}$
✓
Answer
Correct option: B.
$C_2^{2-}$
b
$C_2^{2 - } - {\sigma _{1s}}2{\sigma ^*}_{1s}2{\sigma _{2s}}2{\sigma ^*}_{2{s^2}}[{\pi _{2p_x^2}} = {\pi _2}p_y^2]{\sigma _{2p_z^2}}$
$C_2^{2 - } - {\sigma _{1s}}2{\sigma ^*}_{1s}2{\sigma _{2s}}2{\sigma ^*}_{2{s^2}}[{\pi _{2p_x^2}} = {\pi _2}p_y^2]{\sigma _{2p_z^2}}$
$B.O = \frac{{10 - 4}}{2} = 3$ (diamagnetic)
$N_2^{2 - } - {\sigma _{1s}}2{\sigma ^*}_{1s}2{\sigma _{2s}}2{\sigma ^*}_{2{s^2}}[{\pi _{2p_x^2}} = {\pi _2}p_y^2]{\sigma _{2p_z^2}}[{\pi _{2p_x^1}} = {\pi ^*}_{2p_y^1}]$
$B.O = \frac{{10 - 6}}{2} = 2$ (paramagnetic)
$O_2^{2 - } - {\sigma _{1s}}2{\sigma ^*}_{1s}2{\sigma _{2s}}2{\sigma ^*}_{2s}2{\sigma _{2p_z^2}}[{\pi _{2p_x^2}} = {\pi _2}p_y^2]\,[{\pi _{2p_x^2}} = {\pi ^*}_2p_y^2]$
$B.O = \frac{{10 - 8}}{2} = 1$ (diamagnetic)
${O_2} - {\sigma _{1s}}2{\sigma ^*}_{1s}2{\sigma _{2s}}2{\sigma ^*}_{2s}2{\sigma _{2p_z^2}}\,[{\pi _{2p_x^2}} = {\pi _2}p_y^2]\,[{\pi _{2p_x^2}} = {\pi ^*}_2p_y^2]$
$B.O = \frac{{10 - 6}}{2} = 2$ (paramagnetic)
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