Question

When $\psi_A$ and $\psi_B$ are the wave functions of atomic orbitals, then $\sigma^*$ is represented by :

• A. $\psi_A - 2\psi_B$
• B. $\psi_A - \psi_B$
• C. $\psi_A + 2\psi_B$
• D. $\psi_A + \psi_B$

Answer 1

Answer: (B)

$\psi_A - \psi_B$

Answer 2

The bonding ($\sigma$) and anti-bonding ($\sigma^*$) molecular orbitals are formed by the constructive and destructive interference of atomic orbitals' wave functions.
For an anti-bonding molecular orbital ($\sigma^*$):
$\psi_{\sigma^*} = \psi_A - \psi_B.$
This occurs due to the out-of-phase overlap of the wave functions, leading to a node between the nuclei and a higher energy state.
Thus, $\sigma^*$ is represented by:
$\psi_A - \psi_B.$