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

Which of the following describes a covalent bond?

1. Sharing of a pair of protons between two atoms

2. Attraction between two charged ions

3. Sharing of a pair of electrons between two nuclei

4. Electrostatic attraction between nonmetals

The correct answer is: Sharing of a pair of electrons between two nuclei

A covalent bond is defined as the sharing of a pair of electrons between two atomic nuclei. This type of bond typically forms between nonmetals, where each atom contributes one electron to the bond, allowing both to achieve greater stability through a full outer electron shell. The shared pair of electrons allows both atoms to experience the attraction of the positively charged nuclei, resulting in a stable arrangement. The other choices describe different types of interactions or bonds. For example, the sharing of protons is not a recognized method of bonding. Ions are held together by electrostatic forces, which describe ionic bonding rather than covalent bonding. Additionally, while electrostatic attraction between nonmetals may occur, it doesn’t specifically refer to the mutual sharing of electrons that characterizes covalent bonds. Thus, the description of a covalent bond accurately highlights the fundamental principle of shared electron pairs, making this choice the correct one.