Thus, 252 isotopes ( nuclides) are stable by definition (including tantalum-180m, for which no decay has yet been observed).
Only 90 isotopes are expected to be perfectly stable, and an additional 162 are energetically unstable, but have never been observed to decay.
įor each of the 80 stable elements, the number of the stable isotopes is given. This list depicts what is agreed upon by the consensus of the scientific community as of 2019. However, it is possible that some isotopes that are now considered stable will be revealed to decay with extremely long half-lives (as with 209 No undiscovered elements are expected to be stable therefore, lead is considered the heaviest stable element. Technetium and promethium ( atomic numbers 43 and 61, respectively ) and all the elements with an atomic number over 82 only have isotopes that are known to decompose through radioactive decay. The 83rd element, bismuth, was traditionally regarded as having the heaviest stable isotope, bismuth-209, but in 2003 researchers in Orsay, France, measured the half-life of 209 Of the first 82 elements in the periodic table, 80 have isotopes considered to be stable. The darker more stable isotope region departs from the line of protons (Z) = neutrons (N), as the element number Z becomes larger. Many rare types of decay, such as spontaneous fission or cluster decay, are known. Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, or electron capture. As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus if too many or too few neutrons are present with regard to the optimum ratio, the nucleus becomes unstable and subject to certain types of nuclear decay. Neutrons stabilize the nucleus, because they attract protons, which helps offset the electrical repulsion between protons. These two forces compete, leading to some combinations of neutrons and protons being more stable than others. ( April 2019)Ītomic nuclei consist of protons and neutrons, which attract each other through the nuclear force, while protons repel each other via the electric force due to their positive charge. Please discuss this issue on the article's talk page. Please read the layout guide and lead section guidelines to ensure the section will still be inclusive of all essential details. Please help by moving some material from it into the body of the article. This article's lead section may be too long for the length of the article.
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