Thisbookgrewoutof anongoing efforttomodernizeColgate University’s three-term,introductory,calculus-level physicscourse. Thebookisforthe first term of this course and is intended to help first-year college students make a good transition from high-school physics to university physics. Thebookconcentrates on the physics that explains why we believe that atoms exist and have the properties we ascribe to them. This story line, which motivates much of our professional research, has helped us limit the material presented to a more humane and more realistic amount than is presented in many beginning university physics courses. The theme of atoms also supports the presentation of more non-Newtonian topics and ideas than is customary in the first term of calculus-level physics. We think it is important and desirable to introduce students sooner than usual to some of the major ideas that shape contemporary physicists’ views of the nature and behavior of matter. Here in the second decade of the twenty-first century such a goal seems particularly appropriate. The quantum nature of atoms and light and the mysteries associated with quantum behavior clearly interest our students. By adding and - phasizing more modern content, we seek not only to present some of the physics that engages contemporary physicists but also to attract students to take more physics. Only a few of our beginning physics students come to us sharply focused on physics or astronomy. Nearly all of them, h- ever, have taken physics in high school and found it interesting.