Q91 · CSIR-NET Chemistry, June 2014

Paper: CSIR-NET June 2014 · Subject: Physical Chemistry · Chapter: Quantum Chemistry · Topic: Quantum Chemistry – General · Marks: 2 · Difficulty: Medium

The simplest ground-state VB wave function of a diatomic molecule like HCl is written as $\psi=\psi_{\mathrm{H}}(1 \mathrm{s}, 1) \psi_{\mathrm{Cl}}\left(3 \mathrm{p}_{\mathrm{z}}, 2\right)+\mathrm{B}$ where B stands for
(a)$\psi_{\mathrm{H}}\left(3 \mathrm{p}_{\mathrm{z}}, 2\right) \psi_{\mathrm{Cl}}(1 \mathrm{s}, 1)$
(b)$\psi_{\mathrm{H}}(1 \mathrm{s}, 2) \psi_{\mathrm{Cl}}\left(3 \mathrm{p}_{\mathrm{z}}, 1\right)$
(c)$\psi_{\mathrm{Cl}}(1 \mathrm{s}, 2) \psi_{\mathrm{Cl}}\left(3 \mathrm{p}_{\mathrm{z}}, 1\right)$
(d)$\psi_{\mathrm{Cl}}(1 \mathrm{s}, 2) \psi_{\mathrm{H}}\left(3 \mathrm{p}_{\mathrm{z}}, 1\right)$
Answer
Answer: B ✓ checked by 4AB · confidence high

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

Explanation
The Heitler–London covalent function is symmetrised by exchanging the electron labels: ψ_H(1s,1)ψ_Cl(3p_z,2) + ψ_H(1s,2)ψ_Cl(3p_z,1).

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