AP EAMCET · Chemistry · d and f Block Elements

Which of the following statements are correct?
I. \(\quad \mathrm{P}\) is having least negative electron gain enthalpy among \(\mathrm{P}, \mathrm{S}, \mathrm{Cl}\), and \(\mathrm{F}\)
II. In \(\mathrm{Eu}, \mathrm{Yb}\) Lanthanoid contraction is not observed
III. \(\mathrm{Ce}(\mathrm{OH})_3\) is most basic among lanthanoid hydroxides
IV. The radii of \(\mathrm{Na}\) and \(\mathrm{Na}^{+}\)are \(95 \mathrm{pm}, 186 \mathrm{pm}\) respectively

A I, III, IV only
B II, IV only
C I, III only
D I, II, III only

Verified Solution

Answer & Solution

Correct Answer

(D) I, II, III only

Step-by-step Solution

Detailed explanation

Europium \((\mathrm{Eu})=[\mathrm{Xe}] 4 \mathrm{f}^7 5 \mathrm{~d}^0 6 \mathrm{~s}^2, 185 \mathrm{pm}\) Ytterbium \((\mathrm{Yb})=[\mathrm{Xe}] 4 \mathrm{f}^{14} 5 \mathrm{~d}^0 6 \mathrm{~s}^2, 170 \mathrm{pm}\) In these two elements, the atomic radii do not show expected…

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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$- OH$	$- CN$	$- {CO}_{2} H$	$- {OCH}_{3}$	$- {NHCOCH}_{3}$	$- CHO$
I	II	III	IV	V	VI