A Level Chemistry OCR Practice Exam

Which term describes a bond formed by a shared pair of electrons provided by only one of the bonding atoms?

1. Dative covalent

2. Ionic

3. Polar covalent

4. Sigma bond

The correct answer is: Dative covalent

The correct answer is dative covalent. This term specifically refers to a type of covalent bond where a shared pair of electrons comes from one of the bonding atoms, rather than being contributed equally by both. In a dative covalent bond, one atom donates both electrons in the bond, which is often seen in coordination complexes where a ligand donates its lone pair to a metal ion. The other options represent different types of bonding or characteristics of bonds. Ionic bonds involve the transfer of electrons from one atom to another, leading to the formation of charged ions. Polar covalent bonds are characterized by an unequal sharing of electrons due to differences in electronegativity, resulting in a dipole moment. Sigma bonds are formed by the head-on overlap of atomic orbitals and can involve shared electron pairs from both atoms. However, none of these options accurately describe the unique characteristic of a dative covalent bond where one atom solely provides the bonding electrons.