Q133 / 200 · MHT CET - Medical 2026 (25 April Shift 1) · Chemistry
Identify the geometry of a complex compound $[\text{CoF}_6]^{-3}$.
- ASquare planar
- BTetrahedral
- Correct answerCOctahedral
- DTrigonal pyramidal
Solution
The given complex is $[\text{CoF}_6]^{3-}$.
The central metal atom is Cobalt (Co). Let its oxidation state be $x$.
$x + 6(-1) = -3 \Rightarrow x = +3$
The electronic configuration of Co is $[\text{Ar}] 3d^7 4s^2$.
The electronic configuration of Co$^{3+}$ is $[\text{Ar}] 3d^6$.
Since F$^-$ is a weak field ligand, it does not cause pairing of electrons in the $3d$ orbitals.
The complex undergoes $sp^3d^2$ hybridization to accommodate six F$^-$ ligands.
For a coordination number of 6, the geometry of the complex is octahedral.
Answer: Octahedral
The central metal atom is Cobalt (Co). Let its oxidation state be $x$.
$x + 6(-1) = -3 \Rightarrow x = +3$
The electronic configuration of Co is $[\text{Ar}] 3d^7 4s^2$.
The electronic configuration of Co$^{3+}$ is $[\text{Ar}] 3d^6$.
Since F$^-$ is a weak field ligand, it does not cause pairing of electrons in the $3d$ orbitals.
The complex undergoes $sp^3d^2$ hybridization to accommodate six F$^-$ ligands.
For a coordination number of 6, the geometry of the complex is octahedral.
Answer: Octahedral
Hence, the correct answer is option: 'C'.