Given below are two statements: Statement I: The number of pairs, from the following, in which both the ions are coloured in aqueous solution is 3. $[\ce{Sc^{3+}}, \ce{Ti^{3+}}]$, $[\ce{Mn^{2+}}, \ce{Cr^{2+}}]$, $[\ce{Cu^{2+}}, \ce{Zn^{2+}}]$ and $[\ce{Ni^{2+}}, \ce{Ti^{4+}}]$ Statement II: $\ce{Th^{4+}}$ is the strongest reducing agent among $\ce{Th^{4+}}$, $\ce{Ce^{4+}}$, $\ce{Gd^{3+}}$ and $\ce{Eu^{2+}}$. In the light of the above statements, choose the correct answer from the options given below

(C) Both Statement I and Statement II are false

(A) Statement I is true but Statement II is false

(B) Statement I is false but Statement II is true

(D) Both Statement I and Statement II are true

d and f Block Elements — JEE Main · 2026 · 28 Jan 2026 · Shift 1 Question with Solution

Given below are two statements:

Statement I: The number of pairs, from the following, in which both the ions are coloured in aqueous solution is 3.

[Sc X^{3 +}, Ti X^{3 +}]

[Mn X^{2 +}, Cr X^{2 +}]

[Cu X^{2 +}, Zn X^{2 +}]

and

[Ni X^{2 +}, Ti X^{4 +}]

Statement II:

Th X^{4 +}

is the strongest reducing agent among

Th X^{4 +}

Ce X^{4 +}

Gd X^{3 +}

and

Eu X^{2 +}

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

Answer: (C)

A hydrated ion is coloured only when d\textendash d transitions are possible, i.e. when the d sub-shell is partly filled.

Sc X^{3 +}

(

3 d^{0}

Ti X^{4 +}

(

3 d^{0}

) and

Zn X^{2 +}

(

3 d^{10}

) are colourless, whereas

Ti X^{3 +}

Mn X^{2 +}

Cr X^{2 +}

Cu X^{2 +}

and

Ni X^{2 +}

are coloured. Checking the pairs, both ions are coloured only in

[Mn X^{2 +}, Cr X^{2 +}]

, so just one pair qualifies and the claim of three is wrong. A reducing agent must itself be capable of oxidation;

Th X^{4 +}

already has the stable

5 f^{0}

core and cannot be oxidised further, while

Eu X^{2 +}

readily loses an electron to reach the stable

4 f^{7}

Eu X^{3 +}

and is the strongest reducing agent of the set, so the claim that

Th X^{4 +}

is the strongest reducing agent is also wrong. Both statements are false.

JEE Main · 2026 · 28 Jan 2026 · Shift 1 · Single correct option