Dative Bond Definition (Coordinate Bond)

One atom provides both electrons in a dative bond.
One atom provides both electrons in a dative bond. PASIEKA, Getty Images

A covalent bond forms when two atoms share electrons. The electron pair is attracted to both atomic nuclei, holding them together to form a bond. In a typical covalent bond, each atom supplies an electron to form the bond. A dative bond is a covalent bond between two atoms where one of the atoms provides both electrons that form the bond. A dative bond is also known as a dipolar bond or coordinate bond.

In a diagram, a dative bond is indicated by drawing an arrow pointing from the atom that donates the lone electron pair toward the atom that accepts the pair. The arrow replaces the usual line that indicates a chemical bond.

Dative Bond Example

Dative bonds are commonly seen in reactions involving hydrogen (H) atoms. For example, when hydrogen chloride dissolves in water to make hydrochloric acid, a dative bond is found in the hydronium ion:

H2O + HCl → H3O+ + Cl-

The hydrogen nucleus is transferred to the water molecule to form hydronium, so it does not contribute any electrons to the bond. One the bond is formed, there is no difference between a dative bond and an ordinary covalent bond.