This article describes a nuclear chemistry unit on the Manhattan Project, a research effort that led to the development of the world's first nuclear weapons during World War II. The unit is appropriate for an introductory high school chemistry or physics course and takes from four to six weeks. The unit poses this essential question: "Over the past 300 years, how have discoveries in science led to the development of nuclear energy and bombs?" Addressing this question, students synthesize knowledge of nuclear chemistry, learn how the scientific community came to construct and understand this knowledge, and understand how this knowledge has transformed society. Students learn and practice writing nuclear decay reactions and build toward a conceptual understanding of the pertinent "Next Generation Science Standards" (NGSS Lead States 2013) performance expectations.