Atom

An atom is the primary particle which makes up virtually all matter and elements in the universe. An atom is composed of a varying amount of the subatomic particles protons, neutrons and electrons. As of the 2370s there were 245 variations of atoms in existence. (VOY: Emanations)

Ionized Atoms
Ionized atoms were atoms in which the amount of electrons or energetic charge of the electrons are increased by 1 e