Paper: CSIR-NET June 2013 · Subject: Physical Chemistry · Chapter: Quantum Chemistry · Topic: Quantum Chemistry – General · Marks: 2 · Difficulty: Medium
In the formation of $\mathrm{H_{2}}$ molecules from 2H atoms placed at positions A and B, and separated by a distance $r_{AB}$, a part of special wave function is $\phi_{A}(1) \phi_{A}(2)+\phi_{B}(1) \phi_{B}(2)$
(a)This is a covalent term and is important as $\mathrm{r}_{\mathrm{AB}} \rightarrow \infty$
(b)This is a ionic term and is important as $\mathrm{r}_{\mathrm{AB}} \rightarrow \infty$
(c)This is a covalent term and is important as $\mathrm{r}_{\mathrm{AB}} \rightarrow \infty$
(d)This is a ionic term and is important as $\mathrm{r}_{\mathrm{AB}} \rightarrow \infty$
Answer
Answer: D ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
φ_A(1)φ_A(2) + φ_B(1)φ_B(2) puts both electrons on one atom (H⁺H⁻): the ionic term, significant only at short r_AB and negligible as r_AB → ∞.