Niels Bohr

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Niels Bohr and Atomic Physics Many looked upon Niels Bohr as inspiration for atomic physics. Not only is Niels Bohr credited with the establishment of the structure of the atom, but he also helped to explain the process of nuclear fusion. (Abbott, 1984) Because of his contribution to atomic physics, Niels Bohr is unquestionably one of the most influential people of the twentieth century.

Niels Bohr was born in Copenhagen, Denmark on October 7, 1885. (Abbott, 1984) Niels' father was a professor of physiology at the University of Copenhagen, and this gave Niels a scientific environment to live in that he would remember for the rest of his life. (Hudson, 1992) Niels' very first research project, completed in 1906, determined the surface tension of water. This project was one of his first major achievements, and he earned the gold medal of the Academy of Sciences. (Abbott, 1984) In 1911, Bohr was awarded his doctorate for a theory explaining the behavior of electrons in metals.

(Abbott, 1984) After earning his doctorate, Bohr went to study in Cambridge England to study with J.J. Thomson. Thomson didn't seem to be interested in Bohr's electron theory, so Bohr decided to go somewhere else where his work would be more "important". (Abbott, 1984) In 1912 Bohr started working with Ernest Rutherford to create the structure of the atom in Manchester England. (Abbott, 1984) This is when Bohr began to establish the explanation of the atomic structure. (Abbott, 1984) He created models that showed electrons around rings on every side of the nucleus. (Abbott, 1984) He also determined that an electron couldn't radiate energy when it orbited an atom. (Asimov, 1991) He stayed in Manchester with Rutherford until 1913, and this is where he published his first papers on atomic and molecular structure. (Boorse, Motz, Weaver, 1989) 1913 was possibly one of Bohr's most significant years in his life. In 1913 Bohr returned to his hometown of Copenhagen to start a family with his wife of one year. (Boorse, Motz, Weaver, 1989) When he had returned to Copenhagen in 1913, not many knew who he was and what he was in the process of. Only a sparse number of physicists knew about him, and many of them weren't even interested in his theory. (Boorse, Motz, Weaver, 1989) In the same year, Bohr developed his theory of the atomic structure. He combined some of the principles of the quantum theory to what he saw when the atoms gave off radiation. (Abbott, 1984) He also determined that the electron in the hydrogen atom could take on any number of orbits at different distances from the nucleus. (Asimov, 1991) There was no precedent for Bohr's quantized states of electrons in the atom. In the classical planetary model, the accelerated electrons had to radiate energy. But in Bohr's quantum atom, electrons do not radiate in their stationary states. Clearly, the electrons in Bohr's model were not little particles revolving around the nucleus. In fact, Bohr immediately recognized the inconsistency between his quantum model and any classical picture of electrons in the atom. Even at this early stage, Bohr was beginning to advocate a view of quantum theory devoid of pictures and interpretation. We may talk of quantized orbits, but this should not lull us into thinking of orbiting particles. It's better to speak of electrons existing in a nonpicturable quantized state, and not to think of electrons as particles in that state. (Jones, 1992, pages 148-149) In 1920 Bohr became the director of the Institute of Theoretical Physics in Copenhagen, built especially for him by the authorities of Denmark. (Abbott, 1984) The Institute rapidly became a center for theoretical physicists from throughout the world, many developed Bohr's work there, resulting in the theories of quantum and wave mechanics that more fully explain the behavior of electrons within atoms. (Abbott, 1984, page 25) In 1922 was a year full of accomplishments for Bohr. He won the Nobel Prize for physics. He won this by showing that a person couldn't work out the structure of the atom according to classic physics, but instead by using the quantum theory. (Asimov, 1991) Another thing that had happened was the Institution had discovered a new element called hafnium. (Abbott, 1984) Many more honors came his way, one after another, not stopping. Back at home in Denmark, people appreciated and acknowledged him for all of the work he had done. (Boorse, Motz, Weaver, 1989) In the 1930's, Bohr concentrated more on finding out about nuclear reactions. (Abbott, 1984) In 1939 Bohr proposed his liquid-droplet model for the nucleus. This explained why a heavy nucleus might not be able to sustain fission after getting a neutron. (Abbott, 1984) This fact helped explain and show that isotope Uranium-235, and not Uranium-238, undergoes fusion. (Boorse, Motz, Weaver, 1989) When World War II was happening, Bohr took large steps to try to help. His Institute had become more of a refuge than a study of physics. It was a refuge for all of the scientists trying to escape from Nazi persecution. (Boorse, Motz, Weaver, 1989) Once Denmark fell, Bohr left the institute because he didn't want to cooperate with the Nazis. (Boorse, Motz, Weaver, 1989) He escaped from Denmark to Sweden, and then from Sweden to England. (Boorse, Motz, Weaver, 1989) From England he came to the United States and immediately helped with the development of the atomic bomb. (Abbott, 1984) While helping with the atomic bomb, he was just helping solve physical problems that were going on, but later he started to have a passion for the control of nuclear weapons. (Abbott, 1984) Niels Bohr died on November 16, 1962, but not before he got to publish three volumes of his essays: Atomic Theory and the Description of Nature, Atomic Physics and the Human Knowledge, and Essays 1958-1962 on Atomic Physics and Human Knowledge. (Abbott, 1984) He was in the middle of his scientific experiment, and he was almost done with it, but he died before he had a chance to finish it. (Boorse, Motz, Weaver, 1989) As you can see, Niels Bohr is a very important person. Without Niels Bohr, we may not have a structure of the atom, nuclear fusion, or possibly even the atomic bomb. Niels Bohr really had a passion for what he did. I don't think that we have so many of those scientists around anymore. Our world may have been a lot different if Niels Bohr wouldn't have made so many discoveries. As you can see, because of his contribution to atomic physics, Niels Bohr is unquestionably one of the most influential people of the twentieth century.

Bibliography Abbot, David, ed. The Biographical Dictionary of Scientists: Physics. New York: Peter Bedrick Books, 1984.

Asimov, Isaac. Atom: Journey Across the Subatomic Cosmos. New York: Truman Talley Books, 1991.

Boorse, Henry A., Lloyd Motz, and Jefferson Hane Weaver. The Atomic Scientists: A Biographical History. New York: Wiley Science Editors, 1989.

Hudson, John. The History of Chemistry. New York: Chapman and Hall, 1992.

Jones, Roger S. Physics for the Rest of Us. Chicago: Contemporary Books, 1992.