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Elemental boron is found in small amounts in meteoroids, but chemically uncombined boron is not otherwise found naturally on Earth. Several allotropes exist: amorphous boron is a brown powder; crystalline boron is silvery to black, extremely hard (9.3 on the Mohs scale ), and a poor electrical conductor at room temperature (1.5 × 10 −6 Ω ...
The Earth's crust is one "reservoir" for measurements of abundance. A reservoir is any large body to be studied as unit, like the ocean, atmosphere, mantle or crust. Different reservoirs may have different relative amounts of each element due to different chemical or mechanical processes involved in the creation of the reservoir.
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.
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Boron is found in nature on Earth almost entirely as various oxides of B(III), often associated with other elements. More than one hundred borate minerals contain boron in oxidation state +3. These minerals resemble silicates in some respect, although boron is often found not only in a tetrahedral coordination with oxygen, but also in a ...
A compound semiconductor is a semiconductor compound composed of chemical elements of at least two different species. These semiconductors form for example in periodic table groups 13–15 (old groups III–V), for example of elements from the Boron group (old group III, boron, aluminium, gallium, indium) and from group 15 (old group V, nitrogen, phosphorus, arsenic, antimony, bismuth).
The elements commonly classified as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. [n 4] The status of polonium and astatine is not settled. Most authors recognise one or the other, or both, as metalloids; Herman, Hoffmann and Ashcroft, on the basis of relativistic modelling, predict astatine will be a monatomic metal.
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.