JEE Main 2026 — Chemistry Inorganic Chemistry

2026mcqhard

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 $[Co(H_2 O)_6]^{2+} < [Co(H_2 O)_6]^{3+} < [Co(en)_3]^{3+}$ .

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

Official previous-year question

Held on 2 Apr 2026 · Verified 6 Jul 2026.

Options

A
Both Statement I and Statement II are true
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

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Solution

Statement I:

The third ionization energy ( $IE_3$ ) corresponds to the removal of the third valence electron. Let us look at the electronic configurations of the divalent cations for the given metals:

$Sc^{2+}$ : $[Ar] 3d^{1}$

$Mn^{2+}$ : $[Ar] 3d^{5}$

$Cu^{2+}$ : $[Ar] 3d^{9}$

$Zn^{2+}$ : $[Ar] 3d^{10}$

For $Sc$ , removing the third electron involves taking it from the $3d^{1}$ state, which results in a highly stable noble gas core ( $[Ar]$ ). Hence, $Sc$ has the lowest $IE_3$ .

For $Zn$ , the third electron must be removed from a completely filled, highly stable $3d^{10}$ subshell. Combined with its high effective nuclear charge ( $Z_{eff}$ ) across the 3d series, $Zn$ requires the highest energy for the removal of the third electron.

Thus, Statement I is true.

Statement II:

The Crystal Field Stabilization Energy (CFSE) depends on the magnitude of the crystal field splitting energy ( $\Delta_o$ ), which in turn depends on the oxidation state of the central metal ion and the strength of the ligand.

Oxidation state: A higher oxidation state on the central metal ion leads to a larger $\Delta_o$ . Therefore, the splitting for $Co^{3+}$ complexes is significantly greater than for $Co^{2+}$ complexes. This makes the CFSE of $[Co(H_2O)_6]^{3+}$ greater than that of $[Co(H_2O)_6]^{2+}$ .
Nature of the ligand: Ethylenediamine ( $en$ ) is a strong field bidentate ligand, whereas $H_2O$ is a weak field ligand. According to the spectrochemical series, $en$ causes a much larger splitting than $H_2O$ . Thus, the $\Delta_o$ and CFSE for $[Co(en)_3]^{3+}$ are greater than those for $[Co(H_2O)_6]^{3+}$ .

The overall order of CFSE is:

$[Co(H_2O)_6]^{2+} < [Co(H_2O)_6]^{3+} < [Co(en)_3]^{3+}$

Thus, Statement II is true.

Since both statements are correct, the correct option is (1).

Answer: Both Statement I and Statement II are true

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Solution

Statement I:

The third ionization energy ( $IE_3$ ) corresponds to the removal of the third valence electron. Let us look at the electronic configurations of the divalent cations for the given metals:

$Sc^{2+}$ : $[Ar] 3d^{1}$

$Mn^{2+}$ : $[Ar] 3d^{5}$

$Cu^{2+}$ : $[Ar] 3d^{9}$

$Zn^{2+}$ : $[Ar] 3d^{10}$

For $Sc$ , removing the third electron involves taking it from the $3d^{1}$ state, which results in a highly stable noble gas core ( $[Ar]$ ). Hence, $Sc$ has the lowest $IE_3$ .

Thus, Statement I is true.

Statement II:

Oxidation state: A higher oxidation state on the central metal ion leads to a larger $\Delta_o$ . Therefore, the splitting for $Co^{3+}$ complexes is significantly greater than for $Co^{2+}$ complexes. This makes the CFSE of $[Co(H_2O)_6]^{3+}$ greater than that of $[Co(H_2O)_6]^{2+}$ .
Nature of the ligand: Ethylenediamine ( $en$ ) is a strong field bidentate ligand, whereas $H_2O$ is a weak field ligand. According to the spectrochemical series, $en$ causes a much larger splitting than $H_2O$ . Thus, the $\Delta_o$ and CFSE for $[Co(en)_3]^{3+}$ are greater than those for $[Co(H_2O)_6]^{3+}$ .

The overall order of CFSE is:

$[Co(H_2O)_6]^{2+} < [Co(H_2O)_6]^{3+} < [Co(en)_3]^{3+}$

Thus, Statement II is true.

Since both statements are correct, the correct option is (1).

Answer: Both Statement I and Statement II are true

JEE Main 2026 — Chemistry Inorganic Chemistry

Options

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JEE Main 2026 — Chemistry Inorganic Chemistry

Options

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Solution

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JEE Main Inorganic Chemistry in other years

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Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

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