A mole of complex compound \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}_{3}\) gives 3 mole of ions, when dissolved in water. One mole of the same complex reacts with two mole of \(\mathrm{AgNO}_{3}\) solution to form two mole of \(\mathrm{AgCl}(\mathrm{s}) .\) The structure of the complex is: (a) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right] .2 \mathrm{NH}_{3}\) (b) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] . \mathrm{Cl}_{2}\) (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl} .2 \mathrm{NH}_{3}\) (d) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl}_{2} .2 \mathrm{NH}_{3}\)

Coordination chemistry is a branch of chemistry that involves the study of compounds formed between metal ions and various organic or inorganic ligands. These compounds are known as coordination compounds, and they have a variety of applications in areas such as catalysis, material science, and medicine.

In a coordination compound, the central metal ion is called the coordination center, while the molecules or ions bound to it are called ligands. Ligands are electron donors; they possess lone pairs of electrons which are used to form coordinate covalent bonds with the metal ion.

The number of ligands attached to a metal ion is known as the coordination number, and this can vary depending on the size, charge, and electron configuration of the metal ion, as well as the size and denticity of the ligands. Coordination compounds are typically characterized by their unique properties such as color, magnetic behavior, and ability to form complexes.

Transition metal complexes form a special class of coordination compounds where the central ion is a transition metal. These metals have the unique ability to use their d-orbitals for bonding, which results in a wide diversity of possible structures and properties.

Complexes of transition metals are distinctive for their electronic configurations which enable them to perform specific and often vital roles in many biological and industrial processes. They're commonly used as catalysts due to their ability to adopt multiple oxidation states, allowing for reversible redox reactions.

Transition metal complexes also exhibit geometrical and optical isomerism, making them interesting subjects of study in stereochemistry. The color of these complexes is highly variable and often indicative of the type of ligands bonded to the metal, as well as the geometry of the complex.

In the context of coordination compounds, chlorine can exist either as a part of the coordination sphere or outside of it. When chlorine is inside the coordination sphere, it's not commonly ionizable because it's bound to the central metal ion as a ligand. Conversely, chlorine atoms that are outside the coordination sphere are ionizable, as they exist as counter-ions, which maintain the charge balance of the complex.

The ability of the chlorine to ionize depends on its location in the compound. In a water solution, the coordination sphere generally remains intact due to the strong metal-ligand bonds, while any counter-ions dissociate and become free ions. For example, in the given exercise, the presence of three ions in solution indicates there's one ionizable chlorine atom for every complex ion formed, suggesting the rest of the chlorine is part of the non-ionizing coordination sphere.