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

Which of the following best defines a covalent bond?

1. A weak attraction between atoms

2. A strong attraction between a shared pair of electrons and two nuclei

3. An electrostatic attraction between charged particles

4. A transient interaction between molecules

The correct answer is: A strong attraction between a shared pair of electrons and two nuclei

A covalent bond is best defined as a strong attraction between a shared pair of electrons and two nuclei. In covalent bonding, atoms share electrons to achieve a full outer shell, resulting in a more stable electronic configuration. This sharing allows both atoms to effectively ‘hold’ onto the electrons, leading to the formation of a bond that is characterized by this mutual attraction: the positively charged nuclei of the bonded atoms attract the negatively charged electrons that are shared between them. This definition highlights the key elements of covalent bonds: the involvement of shared electrons and the stability provided by this electron sharing in relation to the atomic nuclei. This is different from other types of interactions, such as electrostatic attractions in ionic bonds, which involve the attraction between charged ions rather than sharing electrons. The description also distinguishes covalent bonds from weaker interactions like transient molecular forces, which do not involve the permanent sharing of electrons and are therefore much less strong.