Question
Which molecule/ion out of the following does not contain unpaired electrons?
A.
$$N_2^ + $$
B.
$${O_2}$$
C.
$$O_2^{2 - }$$
D.
$${B_2}$$
Answer :
$$O_2^{2 - }$$
Solution :
$$N_2^ + \left( {13} \right) = \sigma 1{s^2},{\sigma ^ * }1{s^2},\sigma 2{s^2},$$ $${\sigma ^ * }2{s^2},\pi 2p_x^2 = \pi 2p_y^2,\sigma 2p_z^1$$
$${O_2}\left( {16} \right) = \sigma 1{s^2},{\sigma ^ * }1{s^2},\sigma 2{s^2},$$ $${\sigma ^ * }2{s^2},\sigma 2p_z^2,\pi 2p_x^2 = \pi 2p_y^2,$$ $${\pi ^ * }2p_x^1, = {\pi ^ * }2p_y^1$$
$$O_2^{2 - }\left( {18} \right) = \sigma 1{s^2},{\sigma ^ * }1{s^2},\sigma 2{s^2},$$ $${\sigma ^ * }2{s^2},\sigma 2p_z^2,\pi 2p_x^2 = \pi 2p_y^2,$$ $${\pi ^ * }2p_x^2, = {\pi ^ * }2p_y^2$$
$${B_2}\left( {10} \right) = \sigma 1{s^2},{\sigma ^ * }1{s^2},\sigma 2{s^2},$$ $${\sigma ^ * }2{s^2},\pi 2p_x^1 = \pi 2p_y^1$$
Thus, $$O_2^{2 - }$$ does not contain unpaired electrons.