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

Why is nitrogen gas, N₂, a gas at room temperature?

1. Nitrogen has a giant covalent structure

2. Nitrogen has a simple molecular structure

3. Nitrogen has a network of strong ionic bonds

4. Nitrogen exists as a metallic solid

The correct answer is: Nitrogen has a simple molecular structure

Nitrogen gas, N₂, is a gas at room temperature due to its simple molecular structure. Each nitrogen molecule consists of two nitrogen atoms covalently bonded together. These molecules are held together by weak van der Waals forces, also referred to as London dispersion forces. The strength of these intermolecular forces is significantly weaker than the covalent bonds that hold the atoms within each nitrogen molecule. At room temperature, the energy of the molecules is sufficient to overcome these weak forces, allowing nitrogen to exist in a gaseous state. This contrasts with substances that have strong intermolecular forces, which would remain in liquid or solid states under similar conditions. Other structural types, such as giant covalent structures or networks of strong ionic bonds, would result in solid forms at room temperature due to stronger bonding forces that require more energy to overcome or break apart. A metallic solid would also have entirely different properties, including conductivity and malleability, which nitrogen does not possess. Thus, the simple molecular structure of nitrogen directly contributes to its gaseous state at room temperature.