Read the passage carefully and answer the questions:

The degeneracy of the d orbitals has been removed due to ligand electron-metal electron repulsions in the octahedral complex to yield three orbitals of lower energy, $t_{2g}$ set and two orbitals of higher energy, $e_g$ set. This splitting of the degenerate levels due to the presence of ligands in a definite geometry is termed as crystal field splitting and the energy separation is denoted by Δo. Thus energy of the two $e_g$ orbitals will increase by (3/5) Δo and that of three $t_{2g}$ will decrease by (2/5) Δo. The crystal field splitting Δo depends upon the field produced by the ligand and charge on the metal ion. Some ligands are able to produce strong fields, in which case the splitting will be large, whereas others produce weak fields and consequently result in small splitting of d orbitals. Relative magnitude of crystal field splitting energy Δo and pairing energy, P (energy required for electron pairing in a single orbital) determine the formation of low spin (Δo > P) or high spin (Δo < P) complex. In tetrahedral coordination entity formation, the d-orbital splitting is inverted and is smaller as compared to the octahedral field splitting. The crystal field theory attributes the colour of the complex to d-d transition of the electron. The colour of the coordination compounds depends on the crystal field splitting. In the absence of ligand, crystal field splitting does not occur and hence the substance is colourless.

Choose the correct statement from the following:

$Δ_ο>P$; strong field ligand; low spin complex

The correct answer is Option (1) → $Δ_ο>P$; strong field ligand; low spin complex

In Crystal Field Theory, the electron arrangement in d orbitals depends on the comparison between:

Δo = Octahedral crystal field splitting energy

P = Pairing energy

Case 1: Δo > P

If the crystal field splitting energy is greater than pairing energy, electrons prefer to pair in the lower energy t₂g orbitals rather than occupy higher eg orbitals.

This leads to formation of a low spin complex.

This situation occurs with strong field ligands such as CN⁻, CO, and NH₃.

Case 2: Δo < P

If the splitting energy is smaller than pairing energy, electrons avoid pairing and occupy higher energy orbitals.

This leads to a high spin complex.

This situation occurs with weak field ligands such as F⁻, Cl⁻, Br⁻ and H₂O.

Thus,

Strong field ligand → Δo > P → Low spin complex

Option-wise Explanation

Option 1: Δo > P ; strong field ligand ; low spin complex

Correct. Strong field ligands produce large splitting leading to low spin complexes.

Option 2: Δo > P ; weak field ligand ; low spin complex

Incorrect. Weak field ligands produce small splitting (Δo < P).

Option 3: Δo < P ; weak field ligand ; low spin complex

Incorrect. Δo < P leads to high spin complexes, not low spin.

Option 4: Δo < P ; strong field ligand ; high spin complex

Incorrect. Strong field ligands produce low spin complexes.