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Boron (5 B) naturally occurs as isotopes 10 B and 11 B, the latter of which makes up about 80% of natural boron. There are 13 radioisotopes that have been discovered, with mass numbers from 7 to 21, all with short half-lives, the longest being that of 8 B, with a half-life of only 771.9(9) ms and 12 B with a half-life of 20.20(2) ms.
The abundance of elements in Earth's crust is shown in tabulated form with the estimated crustal abundance for ... boron: B Lithophile 10 (0.001%) 9,400,000 90 thorium:
Neutron cross section of boron (top curve is for 10 B and bottom curve for 11 B) The 10 B isotope is useful for capturing thermal neutrons (see neutron cross section#Typical cross sections). The nuclear industry enriches natural boron to nearly pure 10 B. The less-valuable by-product, depleted boron, is nearly pure 11 B. [149]
05 B boron: 1.0×10 −5: 7.0×10 −6: 9×10 −6: 1.0000×10 −5: 1.5000×10 −5: 06 C carbon: ... Estimated abundance of the elements in the continental crust ...
The abundance of the chemical elements is a measure of the occurrences of the chemical elements relative to all other elements in a given environment. Abundance is measured in one of three ways: by mass fraction (in commercial contexts often called weight fraction), by mole fraction (fraction of atoms by numerical count, or sometimes fraction of molecules in gases), or by volume fraction.
In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from ...
Aluminium, in contrast to boron, is the most abundant metal in the Earth's crust, and the third most abundant element. It composes about 8.2% (82,000 ppm) of the Earth's crust, surpassed only by oxygen and silicon. [41] It is like boron, however, in that it is uncommon in nature as a free element.
An example of cosmic ray spallation is a neutron hitting a nitrogen-14 nucleus in the Earth's atmosphere, yielding a proton, an alpha particle, and a beryllium-10 nucleus, which eventually decays to boron-10. Alternatively, a proton can hit oxygen-16, yielding two protons, a neutron, and again an alpha particle and a beryllium-10 nucleus.