The 60Co source is about 2 cm in diameter and as a result produces a geometric penumbra, making the edge of the radiation field fuzzy. It produces two gamma rays with energies of 1.17 MeV and 1.33 MeV. The primary decay products before 59Co are element 26 ( iron) isotopes and the primary products after are element 28 ( nickel) isotopes.Ĭobalt-60 (Co-60 or 60Co) is a radioactive metal that is used in radiotherapy. The primary decay mode for isotopes with atomic mass unit values less than that of the most abundant stable isotope, 59Co, is electron capture and the primary mode of decay for those of greater than 59 atomic mass units is beta decay. The isotopes of cobalt range in atomic weight from 50 u ( 50Co) to 73 u ( 73Co). This element also has 4 meta states, all of which have half-lives less than 15 minutes. All of the remaining radioactive isotopes have half-lives that are less than 18 hours and the majority of these have half-lives that are less than 1 second. 22 radioisotopes have been characterized with the most stable being 60Co with a half-life of 5.2714 years, 57Co with a half-life of 271.79 days, 56Co with a half-life of 77.27 days, and 58Co with a half-life of 70.86 days. Naturally occurring cobalt is "monoisotopic", i.e. Ĭommon oxidation states of cobalt include +2 and +3, although compounds with oxidation state +1 are also well developed. Cobalt has a hardness of 5.5 on the Mohs scale of mineral hardness. Metallic cobalt commonly presents a mixture of two crystallographic structures hcp and fcc with a transition temperature hcp→fcc of 722 K. Cobalt has a relative permeability two thirds that of iron. Cobalt-60, an artificially produced radioactive isotope of cobalt, is an important radioactive tracer and cancer-treatment agent. Mammals require small amounts of cobalt which is the basis of vitamin B 12. In nature, it is frequently associated with nickel, and both are characteristic ingredients of meteoric iron. The Curie temperature is of 1388 K with 1.6~1.7 Bohr magnetons per atom. Small amounts of it are found in most rocks, soil, water, plants, and animals. Pure cobalt is not found in nature, but compounds of cobalt occur naturally in many forms.
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