Complex Ions

• Complex ions consist of a central metal ion bonded to one or more ligands.
• A ligand is an ion or molecule that can donate a pair of electrons to a metal ion to form a coordinate bond.
• Different ligands have different numbers of electron pairs they can donate, hence affecting the configuration of the complex ion.
• Complex ions can be positively charged, negatively charged, or neutral. The charge depends on the charges of the central metal ion and the ligands.
• The coordination number of a complex ion is the number of coordinate bonds formed between the central metal ion and the ligands. It typically ranges from 2 to 6 but can sometimes be larger.
• Complex ions show a variety of colours. These colours arise from the absorption of certain wavelengths of light that results in electron transitions within the d orbitals of the central metal ion.
• Transition metals can form complex ions due to their ability to form coordinate bonds with ligands and their partially filled d orbitals.
• Some common examples of complex ions include [Fe(H2O)6]3+, [Cu(NH3)4(H2O)2]2+, and [Ni(CN)4]2-.
• The shapes and geometries of complex ions depend on the coordination number and the type of ligands. For example, complexes with a coordination number of 6 usually have an octahedral geometry.
• Complex ions are important in many areas of chemistry including biological systems, industrial processes, and in the formation of colourful compounds.
• Ligand substitution is a common reaction of transition metal complex ions, where one ligand is replaced by another. This can lead to a change in colour.