The central atom or group of atoms will have a positive charge, and the ligands will bond by compensating that charge with their own negative charge or characteristics. As the central atom has a specific charge, it has a maximum potential number of ligands (as each must donate at least one electron into the charge compensation equation) that it can bond to. These ligands will also arrange themselves into a certain arrangement around the central atom. If a single ligand bonds to more than one of these bonding sites on the central atom, then it is said to be bidentate (three=tridentate, etc)
Ligand arrangements
These are named and described as if the central atom is in the middle of a polyhedron, and the corners of that shape are the locations of the ligands. For example, a complex with four, regularly distributed ligands would be described as tetrahedral.
Aside from the regular polyhedra, there are special descriptions, such as pyramidal (four ligands equally distributed in a plane, and one ligand normal to this plane).
Common ligands
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