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Pauli, Wolfgang

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Pauli, Wolfgang (1900-1958), Austrian-born Swiss physicist and Nobel laureate, known for his definition of the exclusion principle in quantum mechanics. He was born in Vienna, and educated at the University of Munich. He taught physics at the Universities of Göttingen (1921-1922), Copenhagen (1922-1923), and Hamburg (1923-1928) and was professor of theoretical physics at the Federal Institute of Technology in Zürich from 1928 until his death in 1958. He also served as visiting professor at the Institute for Advanced Study at Princeton, New Jersey (1935-1936, 1940-1945, 1949-1950, and 1954).

In 1925 Pauli defined the exclusion principle, also called the Pauli exclusion principle, which states that no two electrons can occupy the same quantum state simultaneously in an atom (see Atom and Atomic Theory; Quantum Theory). Four quantum numbers—principle, angular momentum, magnetic, and spin quantum numbers—define the quantum state of an electron. Pauli’s exclusion principle states that no two electrons in the same atom can share all four quantum numbers. Pauli’s hypothesis in 1930 of the existence of the neutrino, a subatomic particle, was a fundamental contribution to the development of meson theory. He was awarded the 1945 Nobel Prize in physics.

Bunsen, Robert Wilhelm

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Bunsen, Robert Wilhelm (1811-1899), German chemist, who, with the German physicist Gustav Robert Kirchhoff, invented the spectroscope and discovered spectrum analysis, which led to their joint discovery of the elements cesium and rubidium.

Bunsen was born in Göttingen on March 31, 1811, and was educated at the University of Göttingen. Between 1836 and 1852 he taught successively at the Polytechnic Institute in Kassel and at the universities of Marburg and Breslau; thereafter he was professor at the University of Heidelberg until his retirement in 1889. Considered one of the greatest chemists in the world, Bunsen discovered (1834) the antidote that is still used today for arsenic poisoning: hydrated iron oxide. His research on the double cyanides confirmed the principle in organic chemistry that the nature of a compound depends on the radicals composing it. Contrary to popular belief, he had little to do with the invention of the Bunsen burner, a gas burner used in scientific laboratories. Although Bunsen improved and popularized the device, credit for its design should go to the British chemist and physicist Michael Faraday. Among Bunsen's inventions are the ice calorimeter, a filter pump, and the zinc-carbon electric cell. He used the cell to produce an electric-arc light and invented a photometer to measure its luminosity. The cell was used also in his development of an electrolytic method of producing metallic magnesium. Results of his research on waste gases of blast furnaces were published in the classic Gasometric Methods (1857). Bunsen died in Heidelberg on August 16, 1899.

Kirchhoff, Gustav Robert

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Kirchhoff, Gustav Robert (1824-87), German physicist, born in Königsberg (now Kaliningrad, Russia), and educated at the University of Königsberg. He was professor of physics at the universities of Breslau, Heidelberg, and Berlin. With the German chemist Robert Wilhelm Bunsen, Kirchhoff developed the modern spectroscope for chemical analysis. In 1860 the two scientists discovered the elements cesium and rubidium by means of spectrum analysis. Kirchhoff conducted important investigations of radiation heat transfer and also postulated two rules, now known as Kirchhoff's laws of networks, concerning the distribution of current in electric circuits.

Davy, Sir Humphry

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Davy, Sir Humphry (1778-1829), renowned British chemist, best known for his experiments in electrochemistry and for his invention of a miner's safety lamp.

Davy was born on December 17, 1778, in Penzance, Cornwall, England. In 1798 he began experiments on the medicinal properties of gases, during which he discovered the anesthetic effects of nitrous oxide (laughing gas). Davy was appointed assistant lecturer in chemistry at the newly founded Royal Institution in London in 1801 and the following year became professor of chemistry there.

During his early years at the Royal Institution, Davy started his investigations of the effects of electricity on chemical compounds. In 1807 he received the Napoleon Prize from the Institut de France for the theoretical and practical work begun the year before. He then constructed the largest battery ever built, with over 250 cells, and passed a strong electric current through solutions of various compounds suspected of containing undiscovered elements. Davy quickly isolated the elements potassium and sodium by this electrolytic method. He also prepared calcium by the same method. In later, unrelated experiments, he discovered boron and proved that the diamond is composed of carbon. Davy also showed that the so-called rare earths are oxides of metals rather than elements. His experiments with acids indicated that hydrogen, not oxygen, causes the characteristics of acids. Davy also made notable discoveries in heat.

In the field of applied science, Davy invented a safety lamp for miners in 1815. For this and for related research, he received the gold and the silver Rumford medals from the Royal Society. In 1823 he suggested a method of preventing the corrosion of the copper bottoms of ships by means of zinc and iron sheathing. He was knighted in 1812 and raised to a baronetcy in 1818. In 1820 he became president of the Royal Society. Davy died on May 29, 1829, in Geneva.

Among his writings are Elements of Chemical Philosophy (1812) and Elements of Agricultural Chemistry (1813).