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VBT for [Ni(CN)₄]²⁻ and its magnetism

Short answer

Ni2+ (3d8) with strong CN- forces electron pairing, vacating one 3d orbital. dsp2 hybridization yields square planar geometry. No unpaired electrons, so the complex is diamagnetic.

Explain the formation of [Ni(CN)₄]²⁻ on the basis of VBT of coordination compounds and predict its magnetic property.

Ni (Z = 28); Ni²⁺ is 3d⁸. CN⁻ is a strong-field ligand.

Formation: the two unpaired 3d electrons are forced to pair, which vacates one 3d orbital. One 3d, one 4s and two 4p orbitals hybridise to form four dsp² orbitals, which accept four CN⁻ lone pairs.

Ni²⁺ 3d: [↑↓][↑↓][↑↓][↑↓][  ]   4s [ ]  4p [ ][ ][ ]
                        \______ dsp² ______/
  • Geometry: square planar.
  • Magnetism: no unpaired electron, so the complex is diamagnetic.

✓ Answer checked by Claude Opus 5.5 (high effort)

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