The correct order of ligands arranged in increasing field strength.

CONCEPT:

Ligand Field Strength (Spectrochemical Series)

• The spectrochemical series arranges ligands in order of increasing field strength (ability to split the d-orbitals of the central metal ion).
• Common ligands have the following approximate order from weakest to strongest:
  • I^– < Br^– < Cl^– < F^– < OH^– < H₂O < NH₃ < CN^–

Explanation:-

• Comparing the experimental order with the given options, the third option is:
  • Br^– < F^– < H₂O < NH₃
  • This matches well with the experimental order and the known spectrochemical series.
• Experimental order  Br– < F– < H2O < NH3 

CONCLUSION:

The correct answer is Br^– < F^– < H₂O < NH₃