Copenhagen, nơi Niels Bohr, một nhà vật lý Đan Mạch, đã nghiên cứu cấu trúc của nguyên tử. Urey quan tâm đến nghiên cứu của Bohr đã được canh tác trong khi nghiên cứu với Lewis, người đã đề xuất nhiều giả thuyết ban đầu về bản chất của liên kết hóa học. Khi trở về Hoa Kỳ vào năm 1925, Urey chấp nhận một cuộc hẹn như một liên kết hóa học tại Đại học Johns Hopkins ở Baltimore | of heat capacities and entropies the degree of randomness in a system of gases based on information obtained through the use of a spectroscope. He then left for a year of postdoctoral study at the Institute for Theoretical Physics at the University of Copenhagen where Niels Bohr a Danish physicist was researching the structure of the atom. Urey s interest in Bohr s research had been cultivated while studying with Lewis who had proposed many early theories on the nature of chemical bonding. Upon his return to the United States in 1925 Urey accepted an appointment as an associate in chemistry at the Johns Hopkins University in Baltimore a post he held until 1929. He interrupted his work at Johns Hopkins briefly to marry Frieda Daum in Lawrence Kansas in 1926. Daum was a bacteriologist and daughter of a prominent Lawrence educator. The Ureys later had four children. In 1929 Urey left Johns Hopkins to become associate professor of chemistry at Columbia University and in 1930 he published his first book Atoms Molecules and Quanta written with A. E. Ruark. Writing in the Dictionary of Scientific Biography Joseph N. Tatarewicz called this work the first comprehensive English language textbook on atomic structure and a major bridge between the new quantum physics and the field of chemistry. At this time he also began his search for an isotope of hydrogen. Since Frederick Soddy an English chemist discovered isotopes in 1913 scientists had been looking for isotopes of a number of elements. Urey believed that if an isotope of heavy hydrogen existed one way to separate it from the ordinary hydrogen isotope would be through the vaporization of liquid hydrogen. Urey s subsequent isolation of deuterium made Urey famous in the scientific world and only three years later he was awarded the Nobel Prize in chemistry for his discovery. During the latter part of the 1930s Urey extended his work on isotopes to other elements besides hydrogen. Urey found that the mass differences in .
