Inert generally means somethings motionless or in a state of doing little or nothing. Noble gases were once called inert gases because they were thought to be completely inert—unable to form compounds. Atomic structure- The atom consists of three component parts: Protons, Neutrons, and Electrons. Electrons- a negatively charged subatomic particle. It can be either free (not attached to any atom), or bound to the nucleus of an atom. Electrons in atoms exist in spherical shells of various radii, representing energy levels. The larger the spherical shell, the higher the energy contained in the electron.