An atom is a type of particle, of which all chemical elements are composed. It has three types of subatomic particles:
- Electrons - carry a negative charge and there are always the same number as protons; they orbit around the nucleus
- Protons - carry a positive charge and are arranged in the center of the atom, the nucleus, with neutrons; the number of protons defines which element the atom is.
- Neutrons - particles with no overall charge that are sited in the nucleus; atoms with the same number of protons but different numbers of neutrons are known as different isotopes.
Atoms can form into molecules by either sharing electrons (covalent bonds) or electrically bonding together (ionic bonds).
In 1930, Edith Keeler gave a speech to the people in the 21st Street Mission, that Humans would soon be able to control great energies, maybe even the atom. Spock remarked, that she envisioned atomic power years before it was developed. (TOS: "The City on the Edge of Forever")
A subject being locked on to by transporter beams from more than one source for an extended period of time could be "ripped apart atom by atom". (DIS: "If Memory Serves")
In 2366, nanites aboard the USS Enterprise-D were built from the atom up. (TNG: "Evolution")