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second
(Encyclopedia)second, abbr. sec or s, fundamental unit of time in all systems of measurement. In practical terms, the second is 1/60 of a minute, 1/3,600 of an hour, or 1/86,400 of a day. Since the length of the da...Pauli, Wolfgang
(Encyclopedia)Pauli, Wolfgang vôlfˈgäng pouˈlē [key], 1900–1958, Austro-American physicist, b. Vienna. He studied first with A. Sommerfeld at Munich and then with Niels Bohr at Copenhagen. After lecturing (1...quantum theory
(Encyclopedia)quantum theory, modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity togethe...electricity
(Encyclopedia) CE5 Electrical and radio symbols electricity, class of phenomena arising from the existence of charge. The basic unit of charge is that on the proton or electron—the proton's charge is designate...activation energy
(Encyclopedia) CE5 Energy profile of an exothermic reaction: Although the total energy of the products is less than that of the reactants, the activation energy must be added to weaken or break existing bonds bef...laser
(Encyclopedia) CE5 Ordinary light sources produce incoherent light, while a laser produces a beam of coherent light. laser [acronym for light amplification by stimulated emission of radiation], device for the cr...water
(Encyclopedia) CE5 A. Water molecule (black circles represent valence-shell electrons) B. Structure of ice: Each oxygen atom (white circles) is bonded to four other oxygen atoms by hydrogen bonds, the hydrogen at...aniline
(Encyclopedia)aniline ănˈəlĭn [key], C6H5NH2, colorless, oily, basic liquid organic compound; chemically, a primary aromatic amine whose molecule is formed by replacing one hydrogen atom of a benzene molecule w...Heck, Richard Fred
(Encyclopedia)Heck, Richard Fred, 1931–2015, American chemist, b. Springfield, Mass., Ph.D. Univ. of California, Los Angeles, 1954. Heck was a researcher at the Hercules Corporation in Wilmington, Del., from 1957...alkyl group
(Encyclopedia)alkyl group ălˈkĭl [key], in chemistry, group of carbon and hydrogen atoms derived from an alkane molecule by removing one hydrogen atom (see radical). The name of the alkyl group is derived from t...Browse by Subject
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