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niobium

(Encyclopedia)niobium nīōˈbēəm [key], metallic chemical element; symbol Nb; at. no. 41; at. wt. 92.90638; m.p. about 2,468℃; b.p. 4,742℃; sp. gr. 8.57 at 20℃; valence +2, +3, +4, or +5. Niobium is a rare...

bohemium

(Encyclopedia)bohemium bōhēˈmēəm [key], former name of the chemical element rhenium. ...

columbium

(Encyclopedia)columbium kəlŭmˈbēəm [key], symbol Cb, former name of the chemical element niobium. ...

francium

(Encyclopedia)francium frănˈsēəm [key] [from France], radioactive chemical element; symbol Fr; at. no. 87; mass no. of most stable isotope 223; m.p. about 27℃ (estimated); b.p. 677℃ (estimated); sp. gr. unk...

vanadium

(Encyclopedia)vanadium vənāˈdēəm [key], metallic chemical element; symbol V; at. no. 23; at. wt. 50.9415; m.p. about 1,890℃; b.p. 3,380℃; sp. gr. about 6 at 20℃; valence +2, +3, +4, or +5. Vanadium is a ...

Wacker process

(Encyclopedia)Wacker process, an industrial process for the manufacture of ethanol by oxidizing ethene. For example, bubbling ethylene and oxygen when treated by an acidified water solution of palladium and cupric ...

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...

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...

californium

(Encyclopedia)californium kălˈĭfôrˌnēəm [key] [from California], artificially produced, radioactive metallic chemical element; symbol Cf; at. no. 98; mass no. of most stable isotope 251; m.p. about 900℃; b...

hafnium

(Encyclopedia)hafnium hăfˈnēəm [key], metallic chemical element; symbol Hf; at. no. 72; at. wt. 178.49; m.p. about 2,227℃; b.p. 4,602℃; sp. gr. 13.31 at 20℃; valence +4. Hafnium is a lustrous, ductile, si...