---
title: "VBT for [Ni(CN)₄]²⁻ and its magnetism"
subject: "Engineering Chemistry"
chapter: 6
key: "semester_2/engineering_chemistry:vbt-nicn4"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/vbt-nicn4
site: BCT Engineering
---

# VBT for [Ni(CN)₄]²⁻ and its magnetism

Engineering Chemistry · Chapter 6: Coordination Complexes

- Asked in: 2072 Magh, 3 marks
- Video: [Ni(CO)4, [Ni(CN)4]2-, [NiCl4]2-Structure-Hybridization-diamagnetic-VBT-IUPAC Name - IIT JEE NEET](https://www.youtube.com/watch?v=r_C4yyTUSjM) — AdiChemistry Aditya Vardhan
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/vbt-nicn4
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-6

## Question

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

## 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.

## Answer

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

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the d configuration of Ni2+ (Z = 28)?
   A. 3d8
   B. 3d10
   C. 3d6
   D. 3d4
   Answer: A. The correct option is: 3d8. This follows from the answer on ni2+. (Key point: Ni2+)

2. What does the strong-field CN- cause in Ni2+ (3d8)?
   A. no pairing
   B. pairing of 3d electrons, vacating one
   C. pairing of 4s
   D. loss of 3d
   Answer: B. The correct option is: pairing of 3d electrons, vacating one. This follows from the answer on pairing. (Key point: Pairing)

3. What hybridisation and shape result in [Ni(CN)4]2-?
   A. sp3 tetrahedral
   B. d2sp3 octahedral
   C. dsp2 square planar
   D. sp3d2
   Answer: C. The correct option is: dsp2 square planar. This follows from the answer on hybrid. (Key point: Hybrid)

4. What is the magnetic behaviour of [Ni(CN)4]2-?
   A. paramagnetic
   B. ferromagnetic
   C. unknown
   D. diamagnetic
   Answer: D. The correct option is: diamagnetic. This follows from the answer on magnet. (Key point: Magnet)

## Related in Engineering Chemistry

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