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insecticides

(Encyclopedia)insecticides, chemical, biological, or other agents used to destroy insect pests; the term commonly refers to chemical agents only. The liabilities of chemical insecticides have encouraged interest ...

sulfur

(Encyclopedia)CE5 Sulfur crystals sulfur or sulphur sŭlˈfər [key], nonmetallic chemical element; symbol S; at. no. 16; interval in which at. wt. ranges 32.059–32.076; m.p. 112.8℃ (rhombic), 119.0℃ (mon...

Butlerov, Aleksandr Mikhailovich

(Encyclopedia)Butlerov, Aleksandr Mikhailovich əlyĭksänˈdər mēkhīlˈəvĭch bo͞otˈlyərôf [key], 1825–86, Russian chemist. As professor at the Univ. of Kazan he founded the first school of Russian chemi...

stereochemistry

(Encyclopedia)stereochemistry, study of the three-dimensional configuration of the atoms that make up a molecule and the ways in which this arrangement affects the physical and chemical properties of the molecule. ...

physical chemistry

(Encyclopedia)physical chemistry, branch of science that combines the principles and methods of physics and chemistry. It provides a fundamental theoretical and experimental basis for all of chemistry, including or...

Zewail, Ahmed Hassan

(Encyclopedia)Zewail, Ahmed Hassan, 1946–2016, Egyptian-American chemist, b. Damanhur, Egypt, Ph.D. Univ. of Pennsylvania, 1974. He became a U.S. citizen in 1982. A professor at the California Institute of Techno...

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...

Athena

(Encyclopedia)Athena pălˈəs [key], in Greek religion and mythology, one of the most important Olympian deities. According to myth, after Zeus seduced Metis he learned that any son she bore would overthrow him, s...

phosphorus

(Encyclopedia)phosphorus fŏsˈfərəs [key] [Gr.,=light-bearing], nonmetallic chemical element; symbol P; at. no. 15; at. wt. 30.97376; m.p. 44.1℃; b.p. about 280℃; sp. gr. 1.82 at 20℃; valence −3, +3, or ...

chlorine

(Encyclopedia)chlorine klōrˈēn, klôrˈ– [key] [Gr.,=green], gaseous chemical element; symbol Cl; at. no. 17; interval in which at. wt. ranges 35.446–35.457; m.p. −100.98℃; b.p. −34.6℃; density 3.2 g...