International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which of the following best describes the nature of a covalent bond?

1. Sharing of protons between two atoms

2. Transfer of electrons from one atom to another

3. Attraction between a shared pair of electrons and two nuclei

4. Formation of a crystal lattice

The correct answer is: Attraction between a shared pair of electrons and two nuclei

A covalent bond is defined as the attraction between a shared pair of electrons and the nuclei of the two atoms involved in the bond. This occurs when two non-metal atoms come closely together and share electrons to achieve a more stable electronic configuration, typically filling their outer electron shells according to the octet rule. The shared electrons create a mutual attraction that holds the atoms together, thus forming a strong bond. This description highlights the essential nature of covalent bonding, where the focus is on the shared electrons rather than on the movement or transfer of electrons that characterize ionic bonding. In ionic bonds, one atom donates electrons to another, leading to the formation of charged ions, which is distinctly different from the concept of covalent bonding. Additionally, the formation of a crystal lattice pertains to ionic compounds rather than covalent bonds, as it describes the organized arrangement of ions in a solid state, which does not apply in the same way to covalent compounds. The sharing of protons is not a mechanism involved in bonding between atoms; instead, protons remain within the atomic nucleus. Hence, the only correct description of a covalent bond focuses on the attraction between shared electrons and the respective nuclei of the atoms involved.