JEE Main 2026 — Chemistry Inorganic Chemistry

2026mcqhard

Given below are two statements :

Statement I : Among $\left.\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+},\left[\mathrm{Ni}(\mathrm{en})_{3}\right)\right]^{2+},\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+}$ and $\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$ , $\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$ has the maximum number of unpaired electrons.

Statement II : The number of pairs among $\left\{\left[\mathrm{NiCl}_{4}\right]^{2-},\left[\mathrm{Ni}(\mathrm{CO})_{4}\right]\right\},\left\{\left[\mathrm{NiCl}_{4}\right]^{2-},\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\right\}$ and $\left\{\left[\mathrm{Ni}(\mathrm{CO})_{4}\right],\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\right\}$ that contain only diamagnetic species is two.

In the light of the above statements, choose the correct answer from the options given below : Statement I is true but Statement II is false Both Statement I and Statement II are false

Official previous-year question

Held on 21 Jan 2026 · Verified 6 Jul 2026.

Options

A
Statement I is true but Statement II is false
B
Both Statement I and Statement II are false
C
Both Statement I and Statement II are true
D
Statement I is false but Statement II is true

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Solution

Statement I: Unpaired electrons in each complex:

$[Cu(NH_3)_4]^{2+}$ : $Cu^{2+}$ is $d^9$ → 1 unpaired

$[Ni(en)_3]^{2+}$ : $Ni^{2+}$ is $d^8$ , octahedral → 2 unpaired

$[Ni(NH_3)_6]^{2+}$ : $Ni^{2+}$ is $d^8$ → 2 unpaired

$[Mn(H_2O)_6]^{2+}$ : $Mn^{2+}$ is $d^5$ , weak field → high spin → 5 unpaired

$[Mn(H_2O)_6]^{2+}$ has maximum. Statement I is true.

Statement II: $[NiCl_4]^{2-}$ : $Ni^{2+}$ ( $d^8$ ), tetrahedral → paramagnetic

$[Ni(CO)_4]$ : $Ni^0$ ( $d^{10}$ ) → diamagnetic

$[Ni(CN)_4]^{2-}$ : $Ni^{2+}$ ( $d^8$ ), square planar → diamagnetic

Only pair $\{[Ni(CO)_4], [Ni(CN)_4]^{2-}\}$ has both diamagnetic. Count = 1, not 2. Statement II is false.

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Solution

Statement I: Unpaired electrons in each complex:

$[Cu(NH_3)_4]^{2+}$ : $Cu^{2+}$ is $d^9$ → 1 unpaired

$[Ni(en)_3]^{2+}$ : $Ni^{2+}$ is $d^8$ , octahedral → 2 unpaired

$[Ni(NH_3)_6]^{2+}$ : $Ni^{2+}$ is $d^8$ → 2 unpaired

$[Mn(H_2O)_6]^{2+}$ : $Mn^{2+}$ is $d^5$ , weak field → high spin → 5 unpaired

$[Mn(H_2O)_6]^{2+}$ has maximum. Statement I is true.

Statement II: $[NiCl_4]^{2-}$ : $Ni^{2+}$ ( $d^8$ ), tetrahedral → paramagnetic

$[Ni(CO)_4]$ : $Ni^0$ ( $d^{10}$ ) → diamagnetic

$[Ni(CN)_4]^{2-}$ : $Ni^{2+}$ ( $d^8$ ), square planar → diamagnetic

Only pair $\{[Ni(CO)_4], [Ni(CN)_4]^{2-}\}$ has both diamagnetic. Count = 1, not 2. Statement II is false.

JEE Main 2026 — Chemistry Inorganic Chemistry

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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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