Read the passage carefully and answer.

The crystal field theory (CFT) is an electrostatic model which considers the metal-ligand bond to be ionic arising purely from electrostatic interactions between the metal ion and the ligand. Ligands are treated as point charges in case of anions or dipoles in case of neutral molecules. The five d orbitals in an isolated gaseous metal atom/ion have same energy, i.e., they are degenerate. This degeneracy is maintained if a spherically symmetrical field of negative charges surrounds the metal atom/ion. However, when this negative field is due to ligands (either anions or the negative ends of dipolar molecules like $NH_3$ and $H_2O$) in a complex, it becomes asymmetrical and the degeneracy of the d orbitals is lifted. It results in splitting of the d orbitals. The pattern of splitting depends upon the nature of the crystal field.

In tetrahedral cordination complexes, low spin configurations are rare because

$Δ_t$ is not sufficienty large to cause pairing.

The correct answer is Option (4) → $Δ_t$ is not sufficienty large to cause pairing.

In tetrahedral coordination complexes:

• The crystal field splitting energy (Δ_t) is much smaller than in octahedral complexes.
• Because Δ_t is small, it cannot overcome the pairing energy, so electrons prefer to remain unpaired.
• Hence, high-spin complexes are formed, and low-spin configurations are rare.

 Correct answer: Δ_t is not sufficiently large to cause pairing.