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calcium
(Encyclopedia)calcium kălˈsēəm [key] [Lat.,=lime], metallic chemical element; symbol Ca; at. no. 20; at. wt. 40.078; m.p. about 839℃; b.p. 1,484℃; sp. gr. 1.55 at 20℃; valence +2. Calcium is a malleable, ...ammonia
(Encyclopedia)ammonia, chemical compound, NH3, colorless gas that is about one half as dense as air at ordinary temperatures and pressures. It has a characteristic pungent, penetrating odor. Ammonia forms a minute ...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...ion, in chemistry
(Encyclopedia)ion, atom or group of atoms having a net electric charge. Ionization has many applications. Vapor lamps and fluorescent lamps take advantage of the light given off when positive ions recombine with ...sewerage
(Encyclopedia)sewerage, system for the removal and disposal of chiefly liquid wastes and of rainwater, which are collectively called sewage. The average person in the industrialized world produces between 60 and 14...formula, in chemistry
(Encyclopedia)formula, in chemistry, an expression showing the chemical composition of a compound. Formulas of compounds are used in writing the equations (see chemical equations) that represent chemical reactions....carpet
(Encyclopedia)carpet or rug, thick fabric, usually woolen (but often synthetic), commonly used today as a floor covering. In North America the Navajos and other tribes have for generations produced substantial ru...volcano
(Encyclopedia)volcano, vents or fissures in the earth's crust through which gases, molten rock, or lava, and solid fragments are discharged. Their study is called volcanology. The term volcano is commonly applied b...nucleus, in physics
(Encyclopedia)nucleus, in physics, the extremely dense central core of an atom. Following the discovery of radioactivity by A. H. Becquerel in 1896, Ernest Rutherford identified two types of radiation given off b...Syria
(Encyclopedia)CE5 Syria sērˈēə [key], officially Syrian Arab Republic, republic (2015 est. pop. 18,735,000), 71,467 sq mi (185,100 sq km), W Asia. It borders on Lebanon and the Mediterranean Sea in the west,...Browse by Subject
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