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tracer

(Encyclopedia)tracer, an identifiable substance used to follow the course of a physical, chemical, or biological process. In chemistry the ideal tracer has the same chemical properties as the molecule it replaces a...

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...

palladium, chemical element

(Encyclopedia)palladium [Gr. Pallas, goddess of wisdom], metallic chemical element; symbol Pd; at. no. 46; at. wt. 106.42; m.p. 1,554℃; b.p. 2,970℃; sp. gr. 12.02 at 20℃; valence +2, +3, or +4. Palladium is a...

Yar'Adua, Umaru Musa

(Encyclopedia)Yar'Adua, Umaru Musa o͞omäˈro͞o mo͞oˈsä yär ädo͞oˈä [key], 1951–2010, Nigerian politician, president of Nigeria (2007–10). Born into a family active in Nigerian political and military ...

tennessine

(Encyclopedia)tennessine tĕnˈəsēn [key], artificially produced radioactive chemical element; symbol Ts; at. no. 117; mass number of most stable isotope 294; m.p., b.p., sp. gr., and valence unknown. Tennessine ...

carboxyl group

(Encyclopedia)carboxyl group kärbŏkˈsĭl [key], in chemistry, functional group that consists of a carbon atom joined to an oxygen atom by a double bond and to a hydroxyl group, OH, by a single bond. Carboxylic a...

Carey, Peter

(Encyclopedia)Carey, Peter, 1943–, Australian novelist, b. near Melbourne. Carey's combination of science fiction and fantasy motifs with a realistic style, displayed in the short stories in The Fat Man in Histor...

livermorium

(Encyclopedia)livermorium, artificially produced radioactive chemical element; symbol Lv; at. no. 116; mass number of most stable isotope 292; m.p., b.p., sp. gr., and valence unknown. Situated in Group 16 of the p...

Merkel, Angela

(Encyclopedia)Merkel, Angela änˈgĕlä märˈkəl [key], 1954–, German politician, b. Hamburg as Angela Dorothea Kasner. The daughter of a Lutheran pastor, she grew up in what was then East Germany. She trained...

amino group

(Encyclopedia)amino group, in chemistry, functional group that consists of a nitrogen atom attached by single bonds to hydrogen atoms, alkyl groups, aryl groups, or a combination of these three. An organic compound...