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uranium

(Encyclopedia)uranium yo͞orāˈnēəm [key], radioactive metallic chemical element; symbol U; at. no. 92; mass number of most stable isotope 238; m.p. 1,132℃; b.p. 3,818℃; sp. gr. 19.1 at 25℃; valence +3, +4...

Levi, Primo

(Encyclopedia)Levi, Primo prēˈmō lāˈvē [key], 1919–87, Italian writer. A chemist of Jewish descent, Levi was sent to the concentration camp at Auschwitz during World War II. His first memoir, If This Is a M...

curium

(Encyclopedia)curium kyo͝orˈēəm [key], artificially produced radioactive chemical element; symbol Cm; at. no. 96; mass no. of most stable isotope 247; m.p. about 1,340℃; b.p. 3,110℃; sp. gr. 13.5 (calculate...

oganesson

(Encyclopedia)oganesson ōˈgənĕsˌən [key], artificially produced radioactive chemical element; symbol Og; at. no. 118; mass number of most stable isotope 294; m.p., b.p., sp. gr., and valence unknown. Situated...

chromium

(Encyclopedia)chromium krōˈmēəm [key] [Gr.,=color], metallic chemical element; symbol Cr; at. no. 24; at. wt. 51.9961; m.p. about 1,857℃; b.p. 2,672℃; sp. gr. about 7.2 at 20℃; valence +2, +3, +6. Chromiu...

europium

(Encyclopedia)europium yo͝orōˈpēəm [key] [from Europe], metallic chemical element; symbol Eu; at. no. 63; at. wt. 151.964; m.p. about 820℃; b.p. about 1,600℃; sp. gr. 5.25 at 25℃; valence +2 or +3. Europ...

thulium

(Encyclopedia)thulium tho͞oˈlēəm [key] [from Thule, an ancient name for Scandinavia], metallic chemical element; symbol Tm; at. no. 69; at. wt. 168.93421; m.p. about 1,545℃; b.p. 1,947℃; sp. gr. 9.3; valenc...

ytterbium

(Encyclopedia)ytterbium ĭtûrˈbēəm [key] [for Ytterby, a town in Sweden], metallic chemical element; symbol Yb; at. no. 70; at. wt. 173.054; m.p. 819℃; b.p. about 1,194℃; sp. gr. about 7.0; valence +2 or +3...

earth, in chemistry

(Encyclopedia)earth, in chemistry, metallic oxide not readily reducible by chemical means, e.g., alkaline earths, rare earths, and alumina. The name is also applied to certain absorbent clays, e.g., fuller's earth,...

thermostat

(Encyclopedia)thermostat, automatic device that regulates temperature in an enclosed area by controlling heating or refrigerating systems. It is commonly connected to one of these systems, turning it on or off in o...