A coordinate bond, also known as a dative covalent bond, is the linkage of two atoms by a pair of electrons, both electrons being provided by one of the atoms (the donor). The coordinate bond is formally identical with the covalent bond. An atom capable of accepting the electrons is the acceptor, the molecule donating the electrons is the donor or ligand. Coordinate linkages occur widely in inorganic complexes.
A coordination compound, also called a complex compound, is a type of chemical compound in which one or more groups or molecules each form a coordinate bond, usually a transition element. The complex may be either a complex ion or a neutral molecule, as in nickel carbonyl (Ni(CO)4). Some coordination compounds, such as heme and chlorophyll, have biological importance.
Chelation is a chemical reaction in which a certain type of organic compound, known as a chelating agent, combines with a metal ion by forming coordinate bonds with two or more atoms of the organic compound. Examples of chelating agents include tartaric acid (CHOHCOOH)2 and ethylenediamine (CH2NH2)2.
The coordination number is the number of chemical bonds made to a central number in a specified complex salt, such as the number of anions (negative ions) surrounding a cation (positive ion).