Niels Bohr proposed a model for the hydrogen atom where the negatively charged electron is attracted to the positively charged proton. Bohr said that electrons move in fixed orbits around the nucleus of the atom. This model is called the planetary model of the atom. He said that the energy of the electron is quantized or electrons may have more than one orbit where each orbit has a characteristic amount of energy. An electron jumps from a lower energy state to a higher energy state when light is absorbed. Light is emitted when the opposite occurs, when the electron falls from a higher energy state to a lower energy state. When Bohr calculated the frequency of light that should be emitted by an excited hydrogen electron changing orbit, his calculations agreed with the experimental results.
Niels Bohr had the first successful interpretation of the hydrogen atom spectrum. He influenced the study of atomic spectra which provided a better understanding of the nature and behavior of light. He was the first to correlate the spectra of an element to the structure of the atom. Bohr stated that the lowest energy state was the most stable state for an atom. He said that because of its stable state that an atom can exist forever; earlier laws of physics predicted that the atom should collapse over time. Niels Bohr was also involved in the development of atomic energy. He helped organize the Atoms for Peace Conference in Geneva and the European Center for Nuclear Research (CERN) in 1955.
Even though the planetary model of the atom only works for the hydrogen atom, Bohr’s theory was instrumental in the discovery of other theories that explain the behavior of electrons in the larger elements. Bohr’s model of fixed orbits paved the way for electron configuration theory.
Bohr proposed the first correct explanation of nuclear fission. His hypothesis said that when an atomic nucleus is struck by another particle, this particle is temporarily incorporated into the nucleus. Thermal energy is concentrated on some particle near the surface of the nucleus. This proton, neutron, or alpha particle then escapes from the nucleus. When a uranium nucleus captures a neutron, the repulsions of the protons tear the nucleus apart into two fragments releasing energy and neutrons. This can result in a chain fission reaction. Bohr also concluded that it is possible to predict nuclear reactions based on information about other reactions.