This monograph was written for the purpose of presenting physics to college students who are not preparing for careers in physics. It deals with the nature of atoms, and treats the following topics: (1) the atomic hypothesis, (2) the chemical elements, (3) models of an atom, (4) a particle in a one-dimensional well, (5) a particle in a central field, (6) angular momentum of a particle in a central field, (7) hydrogen-like atomic states, (8) the building-up principle, (9) the two-electron delta-well atom, and (10) many-electron atoms. All but the first three chapters presuppose an acquaintance with wave mechanics. The monograph is one of a series resulting from the Conference of the Commission on College Physics on the New Instructional Materials in Physics. (DH)