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The most widely studied heavy helium isotope is 8 He. 8 He and 6 He are thought to consist of a normal 4 He nucleus surrounded by a neutron "halo" (of two neutrons in 6 He and four neutrons in 8 He). Halo nuclei have become an area of intense research. Isotopes up to 10 He, with two protons and eight neutrons, have been confirmed.
Helium-4 (4 He) is a stable isotope of the element helium. It is by far the more abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an alpha particle, and consists of two protons and two neutrons.
Helium has two abundant isotopes: helium-3, which is primordial with high abundance in earth's core and mantle, and helium-4, which originates from decay of radionuclides (232 Th, 235,238 U) abundant in the earth's crust. Isotopic ratios of helium are represented by R A value, a value relative to air measurement (3 He/ 4 He = 1.39*10 −6). [98]
Helium is the least water-soluble monatomic gas, [96] and one of the least water-soluble of any gas (CF 4, SF 6, and C 4 F 8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x 2 /10 −5, respectively, versus helium's 0.70797 x 2 /10 −5), [97] and helium's index of refraction is closer to unity than that of any other gas. [98]
is the most common isotope of a common element. This is the case because it is a part of the CNO cycle. The nuclides 6 3 Li and 10 5 B are minority isotopes of elements that are themselves rare compared to other light elements, whereas the other six isotopes make up only a tiny percentage of the natural abundance of their elements.
Of the 26 "monoisotopic" elements that have only a single stable isotope, all but one have an odd atomic number—the single exception being beryllium. In addition, no odd-numbered element has more than two stable isotopes, while every even-numbered element with stable isotopes, except for helium, beryllium, and carbon, has at least three.
The most abundant isotopes -Isotopes with equal numbers of protons and neutrons are unusually abundant. Relative abundance is proportional to the area. (large blue circle) comprises 74% of the ordinary matter of the universe. Color corresponds to nucleosynthetic process: Blue: Big Bang; Green: dying low-mass stars; Yellow: exploding massive stars.
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds. [1]