Question
The electronic configuration of carbon is $$1{s^2}2{s^2}2{p^2}.$$ There are 12 electrons in $${C_2}.$$ The correct electronic configuration of $${C_2}$$ molecule is
A.
$$\left( {\sigma 1{s^2}} \right)\left( {{\sigma ^ * }1{s^2}} \right)\left( {\sigma 2{s^2}} \right)\left( {{\sigma ^ * }2{s^2}} \right)$$ $$\left( {\sigma 2p_z^2} \right)\left( {\pi 2p_x^2} \right)$$
B.
$$\left( {\sigma 1{s^2}} \right)\left( {{\sigma ^ * }1{s^2}} \right)\left( {\sigma 2{s^2}} \right)\left( {{\sigma ^ * }2{s^2}} \right)$$ $$\left( {\pi 2p_x^2 = \pi 2p_y^2} \right)$$
C.
$$\left( {\sigma 1{s^2}} \right)\left( {{\sigma ^ * }1{s^2}} \right)\left( {\sigma 2{s^2}} \right)\left( {{\sigma ^ * }2{s^2}} \right)$$ $$\left( {\sigma 2p_z^2} \right)\left( {\pi 2p_x^1 = \pi 2p_y^1} \right)$$
D.
$$\left( {\sigma 1{s^2}} \right)\left( {{\sigma ^ * }1{s^2}} \right)\left( {\sigma 2{s^2}} \right)\left( {{\sigma ^ * }2{s^2}} \right)$$ $$\left( {\pi 2p_x^2 = \pi 2p_y^1} \right)$$
Answer :
$$\left( {\sigma 1{s^2}} \right)\left( {{\sigma ^ * }1{s^2}} \right)\left( {\sigma 2{s^2}} \right)\left( {{\sigma ^ * }2{s^2}} \right)$$ $$\left( {\pi 2p_x^2 = \pi 2p_y^2} \right)$$
Solution :
For atoms like nitrogen and below $$N$$ in atomic number have higher energy for $${p_z}$$ - orbital, hence the configuration for $${C_2}$$ molecule is $$\left( {\sigma 1{s^2}} \right)\left( {{\sigma ^ * }1{s^2}} \right)\left( {\sigma 2{s^2}} \right)\left( {{\sigma ^ * }2{s^2}} \right)$$ $$\left( {\pi 2p_x^2 = \pi 2p_y^2} \right).$$