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praseodymium

(Encyclopedia)praseodymium prāˌzēōdĭmˈēəm, –sēō– [key] [Gr., =green twin], metallic chemical element; symbol Pr; at. no. 59; at. wt. 140.90765; m.p. 931℃; b.p. 3,512℃; sp. gr. about 6.8; valence +...

structuralism

(Encyclopedia)structuralism, theory that uses culturally interconnected signs to reconstruct systems of relationships rather than studying isolated, material things in themselves. This method found wide use from th...

ruthenium

(Encyclopedia)ruthenium ro͞othēˈnēəm [key], metallic chemical element; symbol Ru; at. no. 44; at. wt. 101.07; m.p. about 2,310℃; b.p. about 3,900℃; sp. gr. 12.41 at 20℃; valence commonly +2, +3, +4, +6, ...

xenon

(Encyclopedia)xenon zēˈnŏn [key] [Gr.,=strange], gaseous chemical element; symbol Xe; at. no. 54; at. wt. 131.293; m.p. −111.9℃; b.p. −107.1℃; density 5.86 grams per liter at STP; valence usually 0. Xeno...

protactinium

(Encyclopedia)protactinium prōˌtăktĭnˈēəm [key], radioactive chemical element; symbol Pa; at. no. 91; mass number of most stable isotope 231; m.p. greater than 1,600℃; b.p. 4,026℃; sp. gr. 15.37 (calcula...

nucleus, in physics

(Encyclopedia)nucleus, in physics, the extremely dense central core of an atom. Following the discovery of radioactivity by A. H. Becquerel in 1896, Ernest Rutherford identified two types of radiation given off b...

nucleosynthesis

(Encyclopedia)nucleosynthesis or nucleogenesis, in astronomy, production of all the chemical elements from the simplest element, hydrogen, by thermonuclear reactions within stars, supernovas, and in the big bang at...

potassium

(Encyclopedia)potassium pətăsˈēəm [key], a metallic chemical element; symbol K [Lat. kalium=alkali]; at. no. 19; at. wt. 39.0983; m.p. 63.25℃; b.p. 760℃; sp. gr. .862 at 20℃; valence +1. Potassium is a s...

symbol

(Encyclopedia)symbol, sign representing something that has an independent existence. The most important use of symbols is in language. To say so, however, does not solve the perennial philosophical questions as to ...

Ingres, Jean Auguste Dominique

(Encyclopedia)Ingres, Jean Auguste Dominique zhäN ōgüstˈ dômēnēkˈ ăNˈgrə [key], 1780–1867, French painter, b. Montauban; son of a sculptor. He studied with J. L. David in Paris and in 1801 won the Prix...