A Level Chemistry OCR Practice Exam

A coordinate bond, also known as a dative bond, specifically refers to a bond in which one atom contributes both electrons to the electron pair that forms the bond. In this situation, one atom has a lone pair of electrons that it can share with another atom, which typically lacks a full complement of electrons. This is different from a typical covalent bond where each atom contributes one electron to the shared pair.

For instance, in the formation of ammonium (NH₄⁺) from ammonia (NH₃) and a proton (H⁺), ammonia donates its lone pair of electrons to the proton, resulting in a coordinate bond. This unique aspect of coordinate bonding is key to understanding many chemical interactions and complex ion formations in chemistry.

The other options do not accurately describe the characteristic of a coordinate bond. Options talking about multiple shared pairs or limitations regarding the types of atoms involved do not capture the essence of how coordinate bonds function.