Final answer:
Nitrogen is the element that is a gas at room temperature from the given list. It exists as a diatomic molecule, N2, and has moderate intermolecular forces in comparison to noble gases which have weaker forces and to solids like antimony and arsenic which have stronger bonds.
Step-by-step explanation:
Among the elements listed (antimony, phosphorus, nitrogen, and arsenic), nitrogen is a gas at room temperature. At 25°C, nitrogen exists as a diatomic molecule (N2) in the atmosphere. Antimony, phosphorus, and arsenic are all solid elements under standard conditions of temperature and pressure. The strength of the forces between atoms within these elements can vary, with noble gases generally having weak Van der Waals forces due to being monatomic, and solids like antimony, phosphorus, and arsenic having stronger covalent or metallic bonds holding their atoms together. Nitrogen, as a diatomic gas, has stronger forces between its atoms than noble gases but weaker than those in solid elements. Among nitrogen, phosphorus, arsenic, and antimony, antimony and arsenic, with their metallic characteristics, likely have the strongest forces between atoms within their structures.