Which atoms never join groups and are considered monoatomic?

The atoms that never join groups and are considered monoatomic are the noble gases, which include helium, neon, argon, krypton, xenon, and radon. These elements have a full valence shell of electrons, making them stable and chemically inert. As a result, they typically do not form bonds with other atoms and exist as single, unbonded atoms in nature.