Monoatomic refers to a single atom.
Noble gases are monatomic gases they are non reactive in nature and do not form any bond with other atoms or molecules.
The noble gases helium, neon, argon, krypton,xenon and radon are monatomic atoms at room temperature and pressure conditions and are gaseous in nature.
The valence shells of these elements are fully filled and have no tendency to accept or denote the outer shell electrons.
Except helium, neon and oganesson, all others have been synthesised by scientists.
Final Answer
The noble gases helium, neon, argon, krypton,xenon and radon are monatomic atoms.