page_title: Cadmium
section_title: Isotopes
hierarchical_section_title: Cadmium / Characteristics / Isotopes
caption_attribution_description: English: The Cd-113 total cross section from ENDF/B-VII. Obtained from the National Nuclear Data Center at Brookhaven National Laboratory.
context_page_description: Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has a lower melting point than the transition metals in groups 3 through 11. Cadmium and its congeners in group 12 are often not considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. The average concentration of cadmium in Earth's crust is between 0.1 and 0.5 parts per million. It was discovered in 1817 simultaneously by Stromeyer and Hermann, both in Germany, as an impurity in zinc carbonate.
  Cadmium occurs as a minor component in most zinc ores and is a byproduct of zinc production. Cadmium was used for a long time as a corrosion-resistant plating on steel, and cadmium compounds are used as red, orange and yellow pigments, to color glass, and to stabilize plastic. Cadmium use is generally decreasing because it is toxic and nickel-cadmium batteries have been replaced with nickel-metal hydride and lithium-ion batteries.
context_section_description: Naturally occurring cadmium is composed of 8 isotopes. Two of them are radioactive, and three are expected to decay but have not done so under laboratory conditions. The two natural radioactive isotopes are ¹¹³Cd (beta decay, half-life is 7.7×10¹⁵ y) and ¹¹⁶Cd (two-neutrino double beta decay, half-life is 2.9×10¹⁹ y). The other three are ¹⁰⁶Cd, ¹⁰⁸Cd (both double electron capture), and ¹¹⁴Cd (double beta decay); only lower limits on these half-lives have been determined. At least three isotopes – ¹¹⁰Cd, ¹¹¹Cd, and ¹¹²Cd – are stable. Among the isotopes that do not occur naturally, the most long-lived are ¹⁰⁹Cd with a half-life of 462.6 days, and ¹¹⁵Cd with a half-life of 53.46 hours. All of the remaining radioactive isotopes have half-lives of less than 2.5 hours, and the majority have half-lives of less than 5 minutes. Cadmium has 8 known meta states, with the most stable being ¹¹³ᵐCd (t1⁄2 = 14.1 years), ¹¹⁵ᵐCd (t1⁄2 = 44.6 days), and ¹¹⁷ᵐCd (t1⁄2 = 3.36 hours).
  The known isotopes of cadmium range in atomic mass from 94.950 u (⁹⁵Cd) to 131.946 u (¹³²Cd). For isotopes lighter than 112 u, the primary decay mode is electron capture and the dominant decay product is element 47 (silver). Heavier isotopes decay mostly through beta emission producing element 49 (indium).
  One isotope of cadmium, ¹¹³Cd, absorbs neutrons with high selectivity: With very high probability, neutrons with energy below the cadmium cut-off will be absorbed; those higher than the cut-off will be transmitted. The cadmium cut-off is about 0.5 eV, and neutrons below that level are deemed slow neutrons, distinct from intermediate and fast neutrons.
  Cadmium is created via the s-process in low- to medium-mass stars with masses of 0.6 to 10 solar masses, over thousands of years. In that process, a silver atom captures a neutron and then undergoes beta decay.
caption: The cadmium-113 total cross section clearly showing the cadmium cut-off
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