Question

The valence electron MO configuration of \( {C}_2 \) (atomic number of C = 6) molecule is:

• A. \( (\sigma 2s)^3 (\sigma^* 2s)^3 (\pi 2p)^2 \)
• B. \( (\sigma 2s)^2 (\sigma^* 2s)^2 (\pi 2p)^4 \)
• C. \( (\sigma 2s)^2 (\sigma^* 2s)^3 (\pi 2p)^3 \)
• D. \( (\sigma 2s)^2 (\sigma^* 2s)^4 (\pi 2p)^2 \)
• E. \( (\sigma 2s)^2 (\sigma^* 2s)^2 (\pi 2p)^5 \)

Hint:

Remember that \( \pi \)-orbitals are filled before \( \pi^* \)-orbitals in molecules where the number of electrons is less than or equal to 8.

Answer 1

The Correct Option is B

The molecular orbital (MO) configuration for \( {C}_2 \) can be determined by filling the molecular orbitals starting from the lowest energy. The energy levels for the \( 2s \) and \( 2p \) orbitals will follow this order: \[ \sigma 2s, \sigma^* 2s, \pi 2p, \pi^* 2p \] For \( {C}_2 \), each carbon atom contributes 4 electrons, giving a total of 8 electrons. According to the MO theory for molecules with even numbers of electrons, the configuration is: \[ (\sigma 2s)^2 (\sigma^* 2s)^2 (\pi 2p)^4 \]