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Robert Wilhelm Eberhard Bunsen (German:; 30 March 1811 [a] – 16 August 1899) was a German chemist.He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with the physicist Gustav Kirchhoff. [11]
Caesium (IUPAC spelling; [9] also spelled cesium in American English) is a chemical element; it has symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C (83.3 °F; 301.6 K), which makes it one of only five elemental metals that are liquid at or near room temperature.
Robert Bunsen (1811–1899), German chemist who discovered caesium in 1860 and rubidium in 1861, pioneer of photochemistry and organoarsenic chemistry and developer of the Bunsen burner Robert F. Christy (1916–2012), Canadian-American theoretical physicist, astrophysicist, one of the last surviving people to have worked on the Manhattan ...
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The first small-scale applications for caesium have been as a "getter" in vacuum tubes and in photoelectric cells. In 1967, a specific frequency from the emission spectrum of caesium-133 was chosen for use in the definition of the second by the International System of Units. Since then, caesium has been widely used in atomic clocks.
Perey discovered it as a decay product of 227 Ac. [177] Francium was the last element to be discovered in nature, rather than synthesized in the lab, although four of the "synthetic" elements that were discovered later (plutonium, neptunium, astatine, and promethium) were eventually found in trace amounts in nature as well. [178]
Margaret Petherbridge Farrar (March 23, 1897 – June 11, 1984) was an American journalist and the first crossword puzzle editor for The New York Times (1942–1968). Creator of many of the rules of modern crossword design, she compiled and edited a long-running series of crossword puzzle books – including the first book of any kind that Simon & Schuster published (1924). [1]
[3] [7] Francium is the second rarest element (after astatine) — only about 550g exists in the entire Earth's crust at any given time — and it was the last element to be discovered in nature. [ 5 ] [ 6 ] (Five elements that were discovered synthetically were later found to exist in nature: technetium , promethium , astatine , neptunium ...