Crystal field theory explains d-d transitions in complexes based on ligand field strength.
Statement I: Ligand field strength order is I⁻ < Br⁻ < Cl⁻ < F⁻. Since Br⁻ is weaker than Cl⁻, [CoBr₄]²⁻ has smaller crystal field splitting (Δ) than [CoCl₄]²⁻. The d-d absorption energy equals the splitting energy, so [CoBr₄]²⁻ absorbs lower energy light. TRUE
Statement II: I⁻ is a much weaker field ligand than Cl⁻. Therefore, [CoI₄]²⁻ has smaller crystal field splitting than [CoCl₄]²⁻, not larger. The energy separation in [CoI₄]²⁻ is less than in [CoCl₄]²⁻. FALSE
Statement I is true but Statement II is false.