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  2. Caesium - Wikipedia

    en.wikipedia.org/wiki/Caesium

    Caesium (IUPAC spelling; [9] also spelled cesium in American English) is a chemical element; it has symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C (83.3 °F; 301.6 K), which makes it one of only five elemental metals that are liquid at or near room temperature .

  3. Caesium-137 - Wikipedia

    en.wikipedia.org/wiki/Caesium-137

    Caesium-137 (137 55 Cs), cesium-137 (US), [7] or radiocaesium, is a radioactive isotope of caesium that is formed as one of the more common fission products by the nuclear fission of uranium-235 and other fissionable isotopes in nuclear reactors and nuclear weapons.

  4. Isotopes of caesium - Wikipedia

    en.wikipedia.org/wiki/Isotopes_of_caesium

    Caesium (55 Cs) has 41 known isotopes, the atomic masses of these isotopes range from 112 to 152. Only one isotope, 133 Cs, is stable. The longest-lived radioisotopes are 135 Cs with a half-life of 1.33 million years, 137 Cs with a half-life of 30.1671 years and 134 Cs with a half-life of 2.0652 years. All other isotopes have half-lives less ...

  5. List of physical constants - Wikipedia

    en.wikipedia.org/wiki/List_of_physical_constants

    atomic mass constant: 1.660 539 068 92 (52) ... hyperfine transition frequency of 133 Cs: 9 192 631 770 Hz: 0 [57] Uncertainties.

  6. Caesium standard - Wikipedia

    en.wikipedia.org/wiki/Caesium_standard

    A caesium atomic fountain used as part of an atomic clock. The caesium standard is a primary frequency standard in which the photon absorption by transitions between the two hyperfine ground states of caesium-133 atoms is used to control the output frequency.

  7. Standard atomic weight - Wikipedia

    en.wikipedia.org/wiki/Standard_atomic_weight

    Atomic weight and relative atomic mass are synonyms. The standard atomic weight is a special value of the relative atomic mass. It is defined as the "recommended values" of relative atomic masses of sources in the local environment of the Earth's crust and atmosphere as determined by the IUPAC Commission on Atomic Weights and Isotopic ...

  8. List of elements by atomic properties - Wikipedia

    en.wikipedia.org/wiki/List_of_elements_by_atomic...

    This is a list of chemical elements and their atomic properties, ... atomic mass Electronegativity (Pauling) First Ionization ... Cs: 132.9054519(2) 0.79: 3.8939 ...

  9. Atomic mass - Wikipedia

    en.wikipedia.org/wiki/Atomic_mass

    Relative atomic mass (Atomic weight) was originally defined relative to that of the lightest element, hydrogen, which was taken as 1.00, and in the 1820s, Prout's hypothesis stated that atomic masses of all elements would prove to be exact multiples of that of hydrogen. Berzelius, however, soon proved that this was not even approximately true ...