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    cesium

    (Encyclopedia) cesium sē´zēəm [key] [Lat.,=bluish gray], a metallic chemical element; symbol Cs; at. no. 55; at. wt. 132.90545; m.p. 28.4°C; b.p. 669.3°C; sp. gr. 1.873 at 20°C; valence +1. Cesium is ...

    Periodic Table of the Elements: Cesium

    (Encyclopedia)Periodic Table of the Elements: CesiumAtomic Number:55Atomic Symbol:Cs CesiumAtomic Weight:132.90545ElectronConfiguration:2 · 8 · 1818 · 8 · 1 ...

    Cs

    (Encyclopedia) Cs, symbol for the element cesium .

    alkali metals

    (Encyclopedia) alkali metals, metals found in Group 1 of the periodic table . Compared to other metals they are soft and have low melting points and densities. Alkali metals are powerful reducing agents...

    Kirchhoff, Gustav Robert

    (Encyclopedia) Kirchhoff, Gustav Robert go͝os´täf rō´bĕrt kĭrkh´hôf [key], 1824–87, German physicist. He served as professor of physics at the universities of Breslau (1850–54), Heidelberg (1854...

    flame test

    (Encyclopedia) flame test, test used in the identification of certain metals. It is based on the observation that light emitted by any element gives a unique spectrum when passed through a spectroscope...

    second

    (Encyclopedia) second, abbr. sec or s, fundamental unit of time in all systems of measurement. In practical terms, the second is 1/60 of a minute, 1/3,600 of an hour, or 1/86,400 of a day. Since the le...

    atomic clock

    (Encyclopedia) atomic clock, electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillat...

    hardness

    (Encyclopedia) hardness, property of matter commonly described as the resistance of a substance to being scratched by another substance. The degree of hardness is relative, different substances being compared...

    United States Naval Observatory

    (Encyclopedia) United States Naval Observatory, a federal astronomical observatory , located in Washington, D. C. It evolved from the Navy's oldest scientific institution, the Depot of Charts and Instru...

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