An alpha nuclide is a nuclide that consists of an integer number of alpha particles. Alpha nuclides have equal, even numbers of protons and neutrons; they are important in stellar nucleosynthesis since the energetic environment within stars is amenable to fusion of alpha particles into heavier nuclei. Stable alpha nuclides, and stable decay products of radioactive alpha nuclides, are some of the most common metals in the universe.
Alpha nuclide is also short for alpha-emitting nuclide, referring to those radioactive isotopes that undergo alpha decay and thereby emit alpha particles.
List of alpha nuclides The entries for 36Ar and 40Ca are theoretical: they would release energy on decay, but the process has never been observed, and the half-lives are probably extremely long. Likewise, the chains for masses 64, 84, 92, and 96 theoretically can continue one more step by double electron capture (to 64Ni, 84Kr, 92Zr, and 96Mo respectively), but this has never been observed. Alpha numberNuclideStabilityDecay modeHalf-lifeProduct(s) of decay (bold is stable)Alpha decay energy(MeV) 1 Stable 2 Radioactive α 8.19(37)×10−17 s +0.09184 3 Stable −7.36659 4 Stable −7.16192 5 Stable −4.72985 6 Stable −9.31656 7 Stable −9.98414 8 Stable −6.94766 9 Observationally Stable (ECEC) never seen () −6.64092 10 Observationally Stable (ECEC) never seen () −7.03978 11 Radioactive EC 60.0(11) y → −5.1271 12 Radioactive β+ 21.56(3) h → −7.698 13 Radioactive β+ 8.275(8) h → −7.936 14 Radioactive β+ 6.075(10) d → −8.0005 15 Radioactive β+ 2.38(5) min → −2.6917 16 Radioactive β+ 63.7(25) s → −2.566 17 Radioactive β+ 35.5(7) s → ... → −2.299 18 Radioactive β+ 17.16(18) s → ... → −2.176 19 Radioactive β+ 7.89(7) s → ... → −2.73 20 Radioactive β+ 4.6(6) s → ... → −3.70 21 Radioactive β+ 3.8(9) ms → ... → −2.71 22 Radioactive β+ 1.3(3) s → ... → −2.27 23 Radioactive β+ 1.1(3) s → ... → −2.28 24 Radioactive β+ 1.003(47) s → ... → −3.03 25 Radioactive β+ 1.1(4) s → ... → −3.47 26 Radioactive α This appears reliable but the NUBASE2020 value is <4 ns and the discrepancy is yet to be explained. → ... → +5.10 27 Radioactive α 58 μs → → ... → +4.57
, the heaviest known alpha nuclide is xenon-108.
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