Q79 · CSIR-NET Chemistry, June 2016

Paper: CSIR-NET June 2016 · Subject: Physical Chemistry · Chapter: Quantum Chemistry · Topic: Hydrogen Atom · Marks: 2 · Difficulty: Medium

In simple molecular orbital theory of hydrogen molecule, bonding $\sigma_{\mathrm{g}}$ and anti-bonding $\sigma_{\mathrm{u}}$ molecular orbitals are constructed as linear combinations of atomic orbitals of two hydrogen atoms. The spatial part of a purely covalent singlet wave function is obtained by

(a)$\sigma_{\mathrm{g}}^{2}+\sigma_{\mathrm{u}}^{2}$

(b)$\sigma_{\mathrm{g}}^{2}$

(c)$\sigma_{\mathrm{g}}^{2}-\sigma_{\mathrm{u}}^{2}$

(d)$\sigma_{\mathrm{g}}^{2}+\frac{1}{2} \sigma_{\mathrm{u}}^{2}$

Answer

Answer: C ✓ checked by 4AB · confidence high

The source book printed no answer; this one was worked out and checked — see the explanation.

Explanation

σg² − σu² ∝ φA(1)φB(2) + φB(1)φA(2): the ionic terms cancel, leaving the Heitler–London covalent function (c).

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