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Astatine is likely to have a dark or lustrous appearance and may be a semiconductor or possibly a metal. Chemically, several anionic species of astatine are known and most of its compounds resemble those of iodine, but it also sometimes displays metallic characteristics and shows some similarities to silver .
The line of stable nuclides down the center of the valley of stability is known as the line of beta stability. The sides of the valley correspond to increasing instability to beta decay (β − or β +). The decay of a nuclide becomes more energetically favorable the further it is from the line of beta stability.
A beta decay mode has been found for all other astatine isotopes except for 212-216 At and their isomers. [ 5 ] [ 1 ] Among other isotopes: astatine-210 and the lighter isotopes decay by positron emission ; astatine-217 and the heavier isotopes undergo beta decay ; and astatine-211 decays by electron capture instead. [ 5 ]
Considering all decay modes, various models indicate a shift of the center of the island (i.e., the longest-living nuclide) from 298 Fl to a lower atomic number, and competition between alpha decay and spontaneous fission in these nuclides; [83] these include 100-year half-lives for 291 Cn and 293 Cn, [55] [78] a 1000-year half-life for 296 Cn ...
Also, the only even neutron numbers with only one beta-decay stable nuclide are 0 (1 H) and 2 (4 He); at least two beta-decay stable nuclides exist for even neutron numbers in the range 4 ≤ N ≤ 160, with exactly two for N = 4 (7 Li and 8 Be), 6 (11 B and 12 C), 8 (15 N and 16 O), 66 (114 Cd and 116 Sn, noting also primordial but not beta ...
It may last for a very long time in this state, but could eventually decay to the more stable one, an event known as false vacuum decay. The most common suggestion of how such a decay might happen in our universe is called bubble nucleation – if a small region of the universe by chance reached a more stable vacuum, this "bubble" (also called ...
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha, beta, and gamma decay.
[33] [34] Superheavy nuclei are thus theoretically predicted [35] and have so far been observed [36] to predominantly decay via decay modes that are caused by such repulsion: alpha decay and spontaneous fission. [g] Almost all alpha emitters have over 210 nucleons, [38] and the lightest nuclide primarily undergoing spontaneous fission has 238. [39]