1. A reference to being based on or involving nuclear reactions: Some atomic references include, atomic reactor (device in which a chain reaction is initiated and controlled, with the resulting heat typically used for power generation and the neutrons and fission products used for military, experimental, and medical purposes) and atomic waste (material containing the unusable radioactive byproducts of the scientific, military, and industrial applications of nuclear energy); plus many other applicable terms.
2. Pertaining to or related to the smallest particle of an element that can exist: Here are some significant atomic terms which are related to atoms.

• Element, a chemical substance that can't be broken down; including solids, liquids, and gases.
• Atom, the smallest particle that keeps its chemical identity.
• Molecule, any collection of two or more atoms that are bound together.
• Electron, an atomic particle that has only a small fraction of the mass of protons and neutrons of the atom.
• Nucleus, the small, massive central part of an atom made from positively charged protons and electrically neutral neutrons.
• Proton, a positively charged nuclear particle consisting of individual electromagnetic waves.
• Neutron, an electrically neutral nuclear particle.
• Ion, an electrically charged atom.

A profession in the area of physics concerned with the scientific structures of the atom, the characteristics of the electrons and other elementary particles of which the atom is composed, the arrangement of the atom's energy states, and the processes involved in the radiation of light and x-rays.