At room temperature, which of these elements exists as diatomic molecules?

• A. Oxygen
• B. Neon
• C. Carbon
• D. Iron

Answer: (A)

Diatomic molecules are made of two atoms bound together. At room temperature, oxygen most commonly exists as a diatomic molecule, O2, because two oxygen atoms share electrons to form a stable double bond, giving a two-atom, covalently bonded molecule. The other elements here don’t exist as diatomic molecules in their standard room-temperature states: neon is a monoatomic noble gas, carbon forms solid covalent networks (like graphite or diamond), and iron is a solid metal arranged in a lattice. So oxygen is the diatomic one.