A coordinate bond is a covalent bond formed between two atoms in which the shared pair of electrons is contributed by only one of the atoms. The atom providing the electron pair is called the donor atom. The atom which accepts the electron pair is called the acceptor atom. A coordinate bond is denoted by an arrow pointing towards the acceptor atom.
Example 10: Formation of ozone molecule (O3)
The electronic configuration of a oxygen atom is 2,6. The two atoms of oxygen share two electrons each to attain a stable configuration, leading to the formation of a double bond between them.