Based on the wavelength of maximum absorption of the cobalt complexes, arrange the following ligands in a spectrochemical series from weakest-field to strongest-field ligand. 
(a) Cl^- < NCS^- < H₂O < NH₃ 
(b) Cl^- < NCS^- < H₂O < NH₃ 
(c) H₂O < Cl^- < NH₃ < NCS^-
(d) Cl^- < H₂O < NCS^- < NH₃

Verified step by step guidance

1. Understand the concept of the spectrochemical series, which ranks ligands based on their ability to split the d-orbitals of a metal ion.
2. Recall that ligands causing a smaller splitting (weak-field ligands) result in longer wavelengths of maximum absorption, while those causing larger splitting (strong-field ligands) result in shorter wavelengths.
3. Identify the typical order of ligands in the spectrochemical series: Cl^- < H2O < NCS^- < NH3.
4. Compare the given options with the typical order to determine which one matches the weakest to strongest field ligands.
5. Select the option that correctly arranges the ligands from weakest-field to strongest-field based on the spectrochemical series.

Key Concepts

Spectrochemical Series

The spectrochemical series is a ranking of ligands based on their ability to split the d-orbitals of transition metal complexes. Ligands that produce a larger splitting of the d-orbitals are considered strong-field ligands, while those that cause less splitting are weak-field ligands. This series helps predict the color and magnetic properties of the complexes formed with different ligands.

Crystal Field Theory

Crystal Field Theory (CFT) explains the electronic structure of transition metal complexes by considering the interaction between the metal ion and surrounding ligands. According to CFT, the presence of ligands causes the degenerate d-orbitals to split into different energy levels, influencing the absorption of light and the resulting color of the complex. Understanding CFT is essential for analyzing how ligands affect the properties of metal complexes.

Ligand Field Strength

Ligand field strength refers to the ability of a ligand to influence the energy levels of the d-orbitals in a transition metal complex. Strong-field ligands, such as NH3 and CN-, cause a greater splitting of the d-orbitals compared to weak-field ligands like Cl-. This concept is crucial for determining the arrangement of ligands in the spectrochemical series and predicting the behavior of the complexes.