An atom with only one electron in its outer orbit is referred to as what?

An atom with only one electron in its outer orbit is referred to as a free radical. Free radicals are species that contain an unpaired electron in their outer shell, which makes them highly reactive. This unpaired electron seeks stability by pairing with another electron, often resulting in reactions with other molecules.

In contrast, ions are atoms that have gained or lost one or more electrons, resulting in a net charge. Molecules are formed when two or more atoms bond together, and isotopes refer to variants of the same element that have the same number of protons but different numbers of neutrons. The unique characteristic of free radicals is that their instability due to the unpaired electron drives them to participate in chemical reactions, which is distinct from the properties of ions, molecules, or isotopes.