Verified Solution • 2025–26 Session moderate

QJEEM25Ch544d: JEE Main 2025 Chemistry - Class 12 JEEM25Ch544d Solution: From the magnetic behaviour of (paramagnetic) and…

From the magnetic behaviour of [NiCl4]2−\left[\mathrm{NiCl}_4\right]^{2-} (paramagnetic) and [Ni(CO)4]\left[\mathrm{Ni}(\mathrm{CO})_4\right] (diamagnetic), choose the correct geometry and oxidation state.

Multiple Choice Options

  • A [NiCl4]2−:Ni(0)\left[\mathrm{NiCl}_4\right]^{2-}: \mathrm{Ni}(0) , tetrahedral [Ni(CO)4]:Ni(0)\left[\mathrm{Ni}(\mathrm{CO})_4\right]: \mathrm{Ni}(0) , square planar
  • B [NiCl4]2−:NiII\left[\mathrm{NiCl}_4\right]^{2-}: \mathrm{Ni}^{\mathrm{II}} , tetrahedral [Ni(CO)4]:Ni(0)\left[\mathrm{Ni}(\mathrm{CO})_4\right]: \mathrm{Ni}(0) , tetrahedral
  • C [NiCl4]2−:NiII\left[\mathrm{NiCl}_4\right]^{2-}: \mathrm{Ni}^{\mathrm{II}} , tetrahedral [Ni(CO)4]:NiII\left[\mathrm{Ni}(\mathrm{CO})_4\right]: \mathrm{Ni}^{I I} , square planar
  • D [NiCl4]2−:NiII\left[\mathrm{NiCl}_4\right]^{2-}: \mathrm{Ni}^{\mathrm{II}} , square planar [Ni(CO)4]:Ni(0)\left[\mathrm{Ni}(\mathrm{CO})_4\right]: \mathrm{Ni}(0) , square planar

Step-by-Step Verified Solution

[NiCl4]2−\left[\mathrm{NiCl}_4\right]^{2-}

Ni+2−[Ar]3 d84 s0→sp3\mathrm{Ni}^{+2}-[\mathrm{Ar}] 3 \mathrm{~d}^8 4 \mathrm{~s}^0 \rightarrow \mathrm{sp}^3 , Tetrahedral

Number of unpaired electron =2=2 paramagentic

[Ni(CO)4]\left[\mathrm{Ni}(\mathrm{CO})_4\right]

Ni(0)→[Ar]3 d104 s0\mathrm{Ni}(0) \rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^0 (After rearrangement)

No unpaired electron

sp3\mathrm{sp}^3 , Tetrahedral, Diamagnetic

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