COMEDK · Chemistry · 3. Classification of Elements and Periodicity in Properties

Among the following, which is not according to the property indicated against it?

A \(\mathrm{I}<\mathrm{Br}<\mathrm{F}<\mathrm{Cl} \text { [Increasing Elecrtron Gain Enthalpy with negative sign] }\)
B \(\mathrm{B}<\mathrm{C}<\mathrm{N}<\mathrm{O} \text { [Increasing First Ionisation Enthalpy] }\)
C \(\mathrm{Mg}^{2+}<\mathrm{Na}^{+}<\mathrm{F}^{-}<\mathrm{O}^{2-} \text { [Increasing Ionic Size] }\)
D \(\mathrm{Na}<\mathrm{K}<\mathrm{Rb}<\mathrm{Cs} \text { [Increasing Metallic Radii] }\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(\mathrm{B}<\mathrm{C}<\mathrm{N}<\mathrm{O} \text { [Increasing First Ionisation Enthalpy] }\)

Step-by-step Solution

Detailed explanation

Correct option is B.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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