Question

which family has a full valence shell, making them the least reactive group of elements? noble gases halogen rare earth metals alkali metals

Explanation:

Noble gases have a full valence - shell configuration which makes them very stable and least reactive. Halogens have 7 valence electrons and are highly reactive to gain one electron for a full shell. Rare earth metals and alkali metals also readily lose electrons to achieve a stable state.

Answer:

noble gases