Search results
Results from the WOW.Com Content Network
Helium-2, 2 He, is extremely unstable. Its nucleus, a diproton, consists of two protons with no neutrons.According to theoretical calculations, it would be much more stable (but still β + decay to deuterium) if the strong force were 2% greater. [18]
It is possible to produce exotic helium isotopes, which rapidly decay into other substances. The shortest-lived heavy helium isotope is the unbound helium-10 with a half-life of 2.6(4) × 10 −22 s. [7] Helium-6 decays by emitting a beta particle and has a half-life of 0.8 second. Helium-7 and helium-8 are created in certain nuclear reactions ...
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]
It contains a table of main isotopes and eventually the standard atomic weight. This template is reused in {{Infobox <element>}} as a child Infobox (|child=yes). As of Jan 2023, a 'Main isotope' is conforming MOS:MAINISOTOPE (under construction, see WP:ELEMENTS What is a "Main_isotope"?) Each isotope has its own row, with decay modes:
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear.
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.
Helium is composed of two electrons bound by the electromagnetic force to a nucleus containing two protons along with two neutrons, depending on the isotope, held together by the strong force. Unlike for hydrogen , a closed-form solution to the Schrödinger equation for the helium atom has not been found.
Isotopes of an element are distinguished by mass number (total protons and neutrons), with this number combined with the element's symbol. IUPAC prefers that isotope symbols be written in superscript notation when practical, for example 12 C and 235 U. However, other notations, such as carbon-12 and uranium-235, or C-12 and U-235, are also used.