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tellurium

(Encyclopedia)tellurium tĕlo͝orˈēəm [key] [Lat.,=earth], semimetallic chemical element; symbol Te; at. no. 52; at. wt. 127.60; m.p. 450℃; b.p. 990℃; sp. gr. 6.24 at 20℃; valence −2, +4, or +6. Telluriu...

selenium

(Encyclopedia)selenium səlēˈnēəm [key], nonmetallic chemical element; symbol Se; at. no. 34; at. wt. 78.96; m.p. 217℃; b.p. about 685℃; sp. gr. 4.81 at 20℃; valence −2, +4, or +6. Selenium is directly ...

germanium

(Encyclopedia)germanium jərmāˈnēəm [key] [from Germany], semimetallic chemical element; symbol Ge; at. no. 32; at. wt. 72.63; m.p. 937.4℃; b.p. 2,830℃; sp. gr. 5.323 at 25℃; valence +2 or +4. Pure german...

sulfide

(Encyclopedia)sulfide, chemical compound containing sulfur and one other element or sulfur and a radical. Sulfides may be salts or esters of hydrogen sulfide, H2S, or may be formed directly, e.g., by heating a meta...

thallium

(Encyclopedia)thallium thălˈēəm [key], metallic chemical element; symbol Tl; at. no. 81; interval in which at. wt. ranges 204.382–204.385; m.p. 303.5℃; b.p. about 1,457℃; sp. gr. 11.85 at 20℃; valence +...

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....

Chemical Ali

(Encyclopedia)Chemical Ali: see Majid, Ali Hassan al-. ...

chemical bond

(Encyclopedia)chemical bond, mechanism whereby atoms combine to form molecules. There is a chemical bond between two atoms or groups of atoms when the forces acting between them are strong enough to lead to the for...

chemical engineering

(Encyclopedia)chemical engineering: see engineering. ...

chemical equation

(Encyclopedia)chemical equation, group of symbols representing a chemical reaction. There are a number of other symbols used in chemical equations. A symbol written above or below the reaction arrow indicates spe...