Answer;
-Noble gases or Group 18 elements
Step-by-step explanation;
A full valence shell is the most stable electron configuration. Group 18 elements or noble gases such as helium, neon, and argon, have a full outer, or valence, shell. Elements in other groups have partially-filled valence shells and gain or lose electrons to achieve a stable electron configuration.
They are extremely unreactive and do not form bonds with themselves. Solid helium is the the ultimate fine powder being monotomic.