A hypothetical second-period diatomic cation A 2 2 + is found to be diamagnetic. If the element A belongs to a group where s − p mixing is usually observed, but for this specific cation, the 2 s − 2

Question

A hypothetical second-period diatomic cation A 2 2 + ​ is found to be diamagnetic. If the element A belongs to a group where s − p mixing is usually observed, but for this specific cation, the 2 s − 2 p energy gap is unexpectedly large (preventing mixing), identify the possible identity of A and the change in Bond Order (BO) if mixing were to occur.

TestHub · Accepted Answer

Question Explanation: Identifying the element and bond order change based on s-p mixing effects. Concept:

Molecular Orbital Theory and s-p mixing.

Solution:

Condition: The cation $A_{2}^{2 +}$ is diamagnetic without s-p mixing.

Analysis of Carbon (C): C has 6 electrons, so $C_{2}^{2 +}$ has $(6 \times 2) - 2 = 10$ electrons.

Without s-p mixing: Order is $σ_{1 s}^{2} σ_{1 s}^{* 2} σ_{2 s}^{2} σ_{2 s}^{* 2} σ_{2 p_{z}}^{2}$ .

$\frac{1}{2} (6 - 4) = 1.0$

With s-p mixing: Order is $σ_{1 s}^{2} σ_{1 s}^{* 2} σ_{2 s}^{2} σ_{2 s}^{* 2} π_{2 p_{x}}^{1} = π_{2 p_{y}}^{1}$ .

$\frac{1}{2} (6 - 4) = 1.0$

The total number of bonding and antibonding electrons does not change, only the identity of the HOMO. $Δ BO : 1.0 - 1.0 = 0$ .

Final Answer: Option (c)

Chemistry - CHEMICAL BONDING Question with Solution | TestHub

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