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twilight
(Encyclopedia)twilight, period between sunset and total darkness or between total darkness and sunrise. Total darkness does not occur immediately when the sun sinks below the horizon because light from the sun that...electrovalent bond
(Encyclopedia)electrovalent bond: see chemical bond. ...ionic bond
(Encyclopedia)ionic bond: see chemical bond.Wayland
(Encyclopedia)Wayland, town (1990 pop. 11,874), Middlesex co., E Mass., W of Boston; settled c.1638, inc. 1835. Electronic and chemical research is carried on there. ...reaction rate
(Encyclopedia)reaction rate: see chemical reaction. ...resonance, in chemistry
(Encyclopedia)resonance, in chemistry: see chemical bond. ...Le Châtelier's principle
(Encyclopedia)Le Châtelier's principle, chemical principle that states that if a system in equilibrium is disturbed by changes in determining factors, such as temperature, pressure, and concentration of components...stannic
(Encyclopedia)stannic: a chemical compound containing tin in the +4 valence state. ...stannous
(Encyclopedia)stannous: a chemical compound containing tin in the +2 valence state. ...activation energy
(Encyclopedia)CE5 Energy profile of an exothermic reaction: Although the total energy of the products is less than that of the reactants, the activation energy must be added to weaken or break existing bonds bef...Browse by Subject
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