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H

(Encyclopedia)H, 8th letter of the alphabet. It is a usual symbol for a glottal spirant, murmured (as in the English house) or voiceless (as in the English herb). In some Greek alphabets eta, the long e, had this f...

Prout, William

(Encyclopedia)Prout, William, 1785–1850, English chemist and physician. Prout's hypothesis, advanced in 1815–16, suggested that atomic weights of elements are multiples of that of hydrogen and that elements are...

peroxide

(Encyclopedia)peroxide pərŏkˈsīd [key], chemical compound containing two oxygen atoms, each of which is bonded to the other and to a radical or some element other than oxygen; e.g., in hydrogen peroxide, H2O2, ...

Haymarket Square riot

(Encyclopedia)Haymarket Square riot, outbreak of violence in Chicago on May 4, 1886. Demands for an eight-hour working day became increasingly widespread among American laborers in the 1880s. A demonstration, large...

electromotive series

(Encyclopedia)electromotive series, list of metals whose order indicates the relative tendency to be oxidized, or to give up electrons (see oxidation and reduction); the list also includes the gas hydrogen. The ele...

fission

(Encyclopedia)fission, in physics: see nuclear energy and nucleus; see also atomic bomb. ...

compound

(Encyclopedia)compound, in chemistry, a substance composed of atoms of two or more elements in chemical combination, occurring in a fixed, definite proportion and arranged in a fixed, definite structure. A compound...

isotope

(Encyclopedia)CE5 Isotopes of hydrogen isotope īˈsətōp [key], in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of ...

chemical equilibrium

(Encyclopedia)chemical equilibrium, state of balance in which two opposing reversible chemical reactions proceed at constant equal rates with no net change in the system. For example, when hydrogen gas, H2, and iod...

cyano group

(Encyclopedia)cyano group sīˈənō, sī-ănˈō [key], in chemistry, functional group that consists of a carbon atom joined to a nitrogen atom by a triple bond; it can be joined to an atom or another group by a s...