d and f Block Elements — JEE Main · 2026 · 02 Apr 2026 · Shift 2 Question with Solution

Given below are two statements:

Statement-I: Among Zn, Mn, Sc and Cu, the energy required to remove the third valence electron is highest for Zn and lowest for Sc.

Statement-II: The correct order of the following complexes in terms of CFSE is

[Co (H X_{2} O) X_{6}]^{2 +} < [Co (H X_{2} O) X_{6}]^{3 +} < [Co (en) X_{3}]^{3 +}

.

In the light of the above statements, choose the correct answer from the options given below:

(A)Both Statement-I and Statement-II are true.✓ Correct
(B)Both Statement-I and Statement-II are false.
(C)Statement-I is true but Statement-II is false.
(D)Statement-I is false but Statement-II is true.

Answer: (A)

Solution

Removing the third electron corresponds to the third ionization enthalpy, and for these metals it rises as

Sc < Mn < Cu < Zn

: scandium loses a

3 d

electron to reach the argon core most readily, whereas zinc must break into its filled

3 d^{10}

shell, which costs the most. Statement-I is therefore correct. For the complexes, crystal field stabilisation grows both with higher oxidation state, which enlarges

Δ_{o}

for

Co X^{3 +}

over

Co X^{2 +}

, and with stronger ligand field, en lying above

H X_{2} O

in the spectrochemical series. This gives

[Co (H X_{2} O) X_{6}]^{2 +} < [Co (H X_{2} O) X_{6}]^{3 +} < [Co (en) X_{3}]^{3 +}

, so Statement-II is also correct. Both statements are true.

JEE Main · 2026 · 02 Apr 2026 · Shift 2 · Single correct option

JEE Main · 2026 · 02 Apr 2026 · Shift 2 · d and f Block Elements

Solution

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