Isotopes of caesium

<p><a href="/facts/Caesium/dXKN1S5k">Caesium</a> (55Cs) has 41 known <a href="/facts/Isotope/KD9B1y6o">isotopes</a>, ranging in <a href="/facts/Mass_number/VyBbJ1oI">mass number</a> from 112 to 152. Only one isotope, 133Cs, is stable. The longest-lived <a href="/facts/Radioisotope/5WpCfbdq">radioisotopes</a> are 135Cs with a half-life of 1.33 million years, <a href="/facts/Caesium-137/NrY5Tb6j">137Cs</a> with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour.
</p><p>Beginning in 1945 with the commencement of <a href="/facts/Nuclear_testing/s2srGDFP">nuclear testing</a>, caesium radioisotopes were released into the <a href="/facts/Earth%2527s_atmosphere/FV97Am25">atmosphere</a>, where caesium is absorbed readily into solution and is returned to the surface of the Earth as a component of <a href="/facts/Radioactive_fallout/I1kJkLKt">radioactive fallout</a>. Once caesium enters the ground water, it is deposited on soil surfaces and removed from the landscape primarily by particle transport. As a result, the input function of these isotopes can be estimated as a function of time.
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Isotopes of caesium open-in-new

Isotopes of caesium