Question

The shape of \( [Ni(CN)_4]^{2- \) is:}

• A. Tetrahedral
• B. Square planar
• C. Octahedral
• D. Trigonal bipyramidal

Hint:

Most \( d^8 \) metal ions with strong field ligands form square planar complexes.

Answer 1

The Correct Option is B

Concept: The geometry of coordination compounds depends upon the metal ion, electronic configuration, and ligand strength.

Step 1: Finding oxidation state of nickel.
In \( [Ni(CN)_4]^{2-} \): \[ x + 4(-1) = -2 \] \[ x - 4 = -2 \] \[ x = +2 \] Thus, nickel is in \( +2 \) oxidation state.

Step 2: Finding electronic configuration.
\[ Ni^{2+} : 3d^8 \]

Step 3: Effect of ligand \( CN^- \).
\( CN^- \) is a strong field ligand. It causes pairing of electrons in \( d \)-orbitals.

Step 4: Determining hybridization and shape.
For \( d^8 \) configuration with strong field ligands: \[ dsp^2 \text{ hybridization occurs} \] This leads to square planar geometry.

Step 5: Final answer.
Hence, the shape is: \[ \boxed{\text{Square planar}} \]