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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.
An estimated 54 billion cubic feet (1.5 × 10 9 m 3) deposit of helium was found in Tanzania in 2016. [152] A large-scale helium plant was opened in Ningxia, China in 2020. [153] In the United States, most helium is extracted from the natural gas of the Hugoton and nearby gas fields in Kansas, Oklahoma, and the Panhandle Field in Texas.
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]
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]
Iron-56 is particularly common, since it is the most stable nuclide (in that it has the highest nuclear binding energy per nucleon) and can easily be "built up" from alpha particles (being a product of decay of radioactive nickel-56, ultimately made from 14 helium nuclei). Elements heavier than iron are made in energy-absorbing processes in ...
Helium also has a very low boiling point (-268.9°C or -452°F), allowing it to remain a gas even in super-cold environments, an important feature because many rocket fuels are stored in that ...
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.