adj. 1 concerned with or using atomic energy or atomic bombs. 2 of or relating to an atom or atoms. atomic bomb = atom bomb. atomic clock a clock in which the periodic process (time scale) is regulated by the vibrations of an atomic or molecular system, such as caesium or ammonia. atomic energy nuclear energy. atomic mass the mass of an atom measured in atomic mass units. atomic mass unit a unit of mass used to express atomic and molecular weights that is equal to one twelfth of the mass of an atom of carbon-12. °Abbr.: amu. atomic number the number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table. °Symb.: Z. atomic particle any one of the particles of which an atom is constituted. atomic philosophy atomism. atomic physics the branch of physics concerned with the structure of the atom and the characteristics of the elementary particles of which it is composed. atomic pile a nuclear reactor. atomic power nuclear power. atomic spectrum the emission or absorption spectrum arising from electron transitions inside an atom and characteristic of the element. atomic structure the structure of an atom as being a central positively charged nucleus surrounded by negatively charged orbiting electrons. atomic theory 1 the concept of an atom as being composed of elementary particles. 2 the theory that all matter is made up of small indivisible particles called atoms, and that the atoms of any one element are identical in all respects but differ from those of other elements and only unite to form compounds in fixed proportions. 3 Philos. atomism. atomic warfare warfare involving the use of atom bombs. atomic weight = relative atomic mass. atomically adv.
[ mod.L atomicus (as ATOM, -IC) ]