AP EAMCET · Chemistry · Classification of Elements and Periodicity in Properties

In which of the following options order of arrangement does not agree with the variation of property indicated against it?

A \(\mathrm{Al}^{3+} < \mathrm{Mg}^{2+} < \mathrm{Na}^{+} < \mathrm{F}\) (increasing ionic size)
B \(\mathrm{B} < \mathrm{C} < \mathrm{O} < \mathrm{N}\) (increasing first ionisation enthalpy)
C l \( < \mathrm{Br} < \mathrm{Cl} < \mathrm{F}\) (increasing electron gain enthalpy)
D \(\mathrm{Li} < \mathrm{Na} < \mathrm{K} < \mathrm{Rb}\) (increasing metallic radius)

Verified Solution

Answer & Solution

Correct Answer

(C) l \( < \mathrm{Br} < \mathrm{Cl} < \mathrm{F}\) (increasing electron gain enthalpy)

Step-by-step Solution

Detailed explanation

Electron gain enthalpy becomes less negative on moving down a group due to increase in atomic size. However, the electron gain enthalpy of \(\mathrm{F}\) is less negative than \(\mathrm{CI}\) due to electron-electron repulsion in small-sized \(\mathrm{F}\) atom. Thus, the…

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.

Same subject

Explore more questions on app

From AP EAMCET

Explore more questions on app