JEE Main · 2026 · 04 Apr 2026 · Shift 1 · d and f Block Elements

The correct statements among the following are,
(A) Mo(VI) and W(VI) are less stable than Cr(VI).
(B)

Ce X^{4 +}

and

Tb X^{4 +}

are oxidant while

Eu X^{2 +}

and

Yb X^{2 +}

are reductant.
(C) Cm and Am have seven unpaired electrons.
(D) Actinoid contraction is greater from element to element than lanthanoid contraction.

Choose the correct answer from the options given below:

(A)A and B Only
(B)C and D Only
(C)B and D Only✓ Correct
(D)A and C Only

Answer: (C)

Solution

Mo(VI) and W(VI) are more stable than the strongly oxidising Cr(VI), so statement (A) is false. In the lanthanoids the

+ 3

state is most stable, so

Ce X^{4 +}

and

Tb X^{4 +}

revert to

+ 3

as oxidants while

Eu X^{2 +}

and

Yb X^{2 +}

revert to

+ 3

as reductants, making statement (B) correct. Curium is

[Rn] 5 f^{7} 6 d^{1} 7 s^{2}

with eight unpaired electrons, not seven, so statement (C) is false. Poor shielding by

5 f

electrons makes the contraction per element larger across the actinoids than across the lanthanoids, so statement (D) is correct. The correct statements are (B) and (D).

JEE Main · 2026 · 04 Apr 2026 · Shift 1 · Single correct option

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JEE Main · 2026 · 04 Apr 2026 · Shift 1 · d and f Block Elements

Solution

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