Niels Bohr was born on October 7, 1885 in Copenhagen, Denmark. Bohr made numerous contributions to our understanding of atomic structure and quantum mechanics. He won the 1922 Nobel Prize for physics, chiefly for his work on the structure of atoms.Bohr received his doctorate in physics from the University of Copenhagen in 1911. He then traveled to Manchester, England to study under British physicist Ernest Rutherford. In 1913 Bohr published a theory about the structure of the atom based on an earlier theory of Rutherford's. Rutherford had shown that the atom consisted of a positively charged nucleus, with negatively charged electrons in orbit around it. Bohr expanded upon this theory by proposing that electrons travel only in certain successively larger orbits. He suggested that the outer orbits could hold more electrons than the inner ones, and that these outer orbits determine the atom's chemical properties. Bohr also described the way atoms emit radiation by suggesting that when an electron jumps from an outer orbit to an inner one, that it emits light. Later other physicists expanded his theory into quantum mechanics. This theory explains the structure and actions of complex atoms.
Bohr became a professor of physics at the University of Copenhagen in 1916. In 1920 Bohr was named director of the newly constructed "Institute of Theoretical Physics" at the University. Bohr became a Fellow of the Royal Society of London in 1926, receiving the Royal Society Copley Medal in 1938. During World War II, Bohr fled Copenhagen to escape the Nazis. He traveled to Los Alamos, New Mexico to advise the scientists developing the first atomic bomb. He returned to Copenhagen after the war and later promoted the peaceful use of atomic energy.