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

Which of the following best describes the bonding in a molecule of oxygen, O₂?

1. Double covalent bond with one lone pair of electrons

2. Single covalent bond with one shared electron

3. Triple covalent bond with no lone pairs

4. Double covalent bond with no lone pairs of electrons

The correct answer is: Double covalent bond with no lone pairs of electrons

In a molecule of oxygen (O₂), the bonding is characterized by a double covalent bond. This occurs because each oxygen atom shares two electrons with the other, resulting in a strong bond that holds the two atoms together. The structure of the O₂ molecule reveals that both oxygen atoms have their outermost electron shells filled through sharing, leading to stability. Specifically, each oxygen has six valence electrons; to achieve a full outer shell (which consists of eight electrons), they share two electrons between them. This sharing results in a double bond. Furthermore, there are no lone pairs of electrons on either of the oxygen atoms after the formation of this double bond, as all the valence electrons participate in bonding. The absence of lone pairs contributes to the stability and shape of the molecule, which is linear due to the double bond. Understanding this bonding type is crucial because it illustrates how atoms can achieve stability by sharing electrons, a fundamental concept in covalent bonding.