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atomic number

(Encyclopedia)atomic number, often represented by the symbol Z, the number of protons in the nucleus of an atom, as well as the number of electrons in the neutral atom. Atoms with the same atomic number make up a c...

Seaborg, Glenn Theodore

(Encyclopedia)Seaborg, Glenn Theodore sēˈbôrg [key], 1912–99, American chemist, b. Ishpeming, Mich., grad. Univ. of California at Los Angeles, 1934, Ph.D. Univ. of California at Berkeley, 1937. In 1939, he beg...

chemical reaction

(Encyclopedia)chemical reaction, process by which one or more substances may be transformed into one or more new substances. Energy is released or is absorbed, but no loss in total molecular weight occurs. When, fo...

roentgenium

(Encyclopedia)roentgenium, artificially produced radioactive chemical element; symbol Rg; at. no. 111; mass number of most stable isotope 280; m.p., b.p., sp. gr., and valence unknown. Situated in Group 11 of the p...

flerovium

(Encyclopedia)flerovium, artificially produced radioactive chemical element; symbol Fl; at. no. 114; mass number of most stable isotope 289; m.p., b.p., sp. gr., and valence unknown. Situated in Group 14 of the per...

Whately, Richard

(Encyclopedia)Whately, Richard hwātˈlē [key], 1787–1863, English prelate and writer. Fellow and tutor of Oriel College, Oxford, he published a witty work aimed at extreme skeptics, Historic Doubts Relative to ...

darmstadtium

(Encyclopedia)darmstadtium, artificially produced radioactive chemical element; symbol Ds; at. no. 110; mass number of most stable isotope 281; m.p., b.p., sp. gr., and valence unknown. Situated in Group 10 of the ...

Moseley, Henry Gwyn Jeffreys

(Encyclopedia)Moseley, Henry Gwyn Jeffreys mōzˈlē [key], 1887–1915, English physicist, grad. Trinity College, Oxford, 1910. He began his research under Ernest Rutherford while serving as lecturer at the Univ. ...

Euclid, Greek mathematician

(Encyclopedia)Euclid yo͞oˈklĭd [key], fl. 300 b.c., Greek mathematician. Little is known of his life other than the fact that he taught at Alexandria, being associated with the school that grew up there in the l...

atomic weight

(Encyclopedia)atomic weight, mean (weighted average) of the masses of all the naturally occurring isotopes of a chemical element, as contrasted with atomic mass, which is the mass of any individual isotope. Althoug...