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ruthenium

(Encyclopedia)ruthenium ro͞othēˈnēəm [key], metallic chemical element; symbol Ru; at. no. 44; at. wt. 101.07; m.p. about 2,310℃; b.p. about 3,900℃; sp. gr. 12.41 at 20℃; valence commonly +2, +3, +4, +6, ...

photochemistry

(Encyclopedia)photochemistry, study of chemical processes that are accompanied by or catalyzed by the emission or absorption of visible light or ultraviolet radiation. A molecule in its ground (unexcited) state can...

rhenium

(Encyclopedia)rhenium rēˈnēəm [key], metallic chemical element; symbol Re; at. no. 75; at. wt. 186.207; m.p. about 3,180℃; b.p. about 5,625℃; sp. gr. 21.02 at 20℃; valence −1, +2, +3, +4, +5, +6, or +7....

actinium

(Encyclopedia)actinium ăktĭnˈēəm [key] [Gr.,=like a ray], radioactive chemical element; symbol Ac; at. no. 89; mass number of most stable isotope 227; m.p. about 1,050℃; b.p. 3,200℃±300℃; sp. gr. 10.07;...

polonium

(Encyclopedia)polonium pəlōˈnēəm [key], radioactive chemical element; symbol Po; at. no. 84; mass no. of most stable isotope 209; m.p. 254℃; b.p. 962℃; sp. gr. about 9.4; valence +2 or +4. Polonium is an e...

oxide

(Encyclopedia)oxide, chemical compound containing oxygen and one other chemical element. Oxides are widely and abundantly distributed in nature. Water is the oxide of hydrogen. Silicon dioxide is the major componen...

periodic law

(Encyclopedia)periodic law, statement of a periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number. Such an arrangement in the for...

Diels, Otto Paul Hermann

(Encyclopedia)Diels, Otto Paul Hermann, 1876–1954, German chemist, Ph.D. Univ. of Berlin, 1899. From 1899 to 1915, Diehls was on the faculty at the Univ. of Berlin. In 1916, he joined the Univ. of Kiel, where he ...

Almería

(Encyclopedia)Almería älmārēˈä [key], city, capital of Almería prov., SE Spain, in Andalusia, on the Gulf of Almería. A busy Mediterranean port, it exports the celebrated grapes...

Hofmann, August Wilhelm von

(Encyclopedia)Hofmann, August Wilhelm von ouˈgo͝ost vĭlˈhĕlm fən hôfˈmän [key], 1818–92, German organic chemist. He was professor at the Univ. of Berlin from 1865 and was a founder (1868) of the German C...