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Cerium is a chemical element; it has symbol Ce and atomic number 58. It is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the oxidation state of +3 characteristic of the series, it also has a stable +4 state that does not oxidize water.
Isotopes of cerium. Naturally occurring cerium (58 Ce) is composed of 4 stable isotopes: 136 Ce, 138 Ce, 140 Ce, and 142 Ce, with 140 Ce being the most abundant (88.48% natural abundance) and the only one theoretically stable; 136 Ce, 138 Ce, and 142 Ce are predicted to undergo double beta decay but this process has never been observed.
Isotopes of praseodymium. Naturally occurring praseodymium (59 Pr) is composed of one stable isotope, 141 Pr. Thirty-eight radioisotopes have been characterized with the most stable being 143 Pr, with a half-life of 13.57 days and 142 Pr, with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less ...
Response evaluation criteria in solid tumors (RECIST) is a set of published rules that define when tumors in cancer patients improve ("respond"), stay the same ("stabilize"), or worsen ("progress") during treatment. The criteria were published in February 2000 by an international collaboration including the European Organisation for Research ...
Isotopes of silicon (14Si) Silicon (14 Si) has 23 known isotopes, with mass numbers ranging from 22 to 44. 28 Si (the most abundant isotope, at 92.23%), 29 Si (4.67%), and 30 Si (3.1%) are stable. The longest-lived radioisotope is 32 Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately ...
Many of these in theory could decay through spontaneous fission, alpha decay, double beta decay, etc. with a very long half-life, but no radioactive decay has yet been observed. Thus, the number of stable nuclides is subject to change if some of these 251 are determined to be very long-lived radioactive nuclides in the future.
There are 28 known radioactive isotopes and 8 nuclear isomers, the most stable of which are 60 Fe (half-life 2.6 million years) and 55 Fe (half-life 2.7 years). Much of the past work on measuring the isotopic composition of iron has centered on determining 60 Fe variations due to processes accompanying nucleosynthesis (i.e., meteorite studies ...
Isotopes of tin. Tin (50 Sn) is the element with the greatest number of stable isotopes (ten; three of them are potentially radioactive but have not been observed to decay). This is probably related to the fact that 50 is a " magic number " of protons. In addition, twenty-nine unstable tin isotopes are known, including tin-100 (100 Sn ...
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