The group with the smallest atomic radius is Group 1, also known as the alkali metals. The elements in this group include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). All of these elements have a single valence electron in their outermost orbital, which makes them highly reactive. As a result, they are all found in nature either in compounds or as minerals.
