Bohr Niels Henrik David

Bohr

 (bôr), Niels Henrik David 1885-1962.
Danish physicist who won a 1922 Nobel Prize for developing a new model of atomic structure. His son Aage Niels Bohr (1922-2009), also a physicist, shared a 1975 Nobel Prize for his work on the structure of atomic nuclei.

Bohr

(bôr), Niels Henrik David 1885-1962.
Danish physicist who investigated atomic structure and radiation. Bohr discovered that electrons orbit the nucleus of an atom at set distances, changing levels only when energy is lost or gained, and emitting or absorbing radiation in the process. His concepts were fundamental to the later development of quantum mechanics.
Biography Before 1911 scientists thought that atoms were organized a bit like a plum pudding, with a mixture of electrons, protons, and neutrons loosely stuck together. Then Ernest Rutherford discovered the atomic nucleus and developed a model of the atom that was similar to the solar system, with negatively charged electrons orbiting a central nucleus the way planets revolve around the sun. Niels Bohr became interested in Rutherford's model, but it puzzled him because according to the laws of physics it should be very unstable. In trying to explain why it was not, Bohr proposed that the electrons could travel only in specific, successively larger orbits around the nucleus. Any increase or decrease in an electron's energy meant that the electron changed place, jumping to a higher or lower orbit. Bohr assumed that when an electron jumps from an outer orbit to an inner one, it emits light. His theory explained the way light is given off by hydrogen, the simplest atom, when its electron drops from a higher orbit to a lower one. Other scientists later expanded Bohr's theory into quantum mechanics.
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