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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...

X ray

(Encyclopedia)CE5 Typical X-ray composite spectrum (intensity as a function of frequency) X ray, invisible, highly penetrating electromagnetic radiation of much shorter wavelength (higher frequency) than visibl...

Quetzalcoatl

(Encyclopedia)Quetzalcoatl kĕtˌsälkôätˈəl [key] [Nahuatl,=feathered serpent], ancient deity and legendary ruler of the Toltec in Mexico. The name is also that of a Toltec ruler, who is credited with the disc...

geology

(Encyclopedia)geology, science of the earth's history, composition, and structure, and the associated processes. It draws upon chemistry, biology, physics, astronomy, and mathematics (notably statistics) for suppor...

water

(Encyclopedia)CE5 A. Water molecule (black circles represent valence-shell electrons) B. Structure of ice: Each oxygen atom (white circles) is bonded to four other oxygen atoms by hydrogen bonds, the hydrogen at...

liverwort

(Encyclopedia)liverwort, any plant of the class Marchantiopsida. Mosses and liverworts together comprise the division Bryophyta, primitive green land plants (see moss; plant); some of the earliest land plants resem...

Mulisch, Harry

(Encyclopedia)Mulisch, Harry mo͞oˈlĭsh [key], 1927–2010, Dutch writer. In the 1960s Mulisch became a prominent member of Amsterdam's new left. He was extremely prolific, writing fiction, nonfiction, and poetry...

Nagel, Ernest

(Encyclopedia)Nagel, Ernest, 1901–85, American philosopher, b. Nové Město (now in the Czech Republic), grad. College of the City of New York, 1923, and Columbia (Ph.D., 1930). His family emigrated to the United...

Lehn, Jean-Marie

(Encyclopedia)Lehn, Jean-Marie zhäNˈ-märēˈ lĕN [key], 1939–, French chemist, Ph.D. Univ. of Strasbourg, 1963. A professor at Louis Pasteur Univ. (1970–78) and the Collège de France (1979–), Lehn did gr...

chemical analysis

(Encyclopedia)chemical analysis, the study of the chemical composition and structure of substances. More broadly, it may be considered the corpus of all techniques whereby any exact chemical information is obtained...