Download Boron is produced by cosmic ray spallation, is a metalloid, and is

Boron is produced by cosmic ray spallation, is a metalloid, and is
essential to life.
LEARNING OBJECTIVE [ edit ]
Review the properties and uses of elemental boron.
KEY POINTS [ edit ]
Chemically uncombined boron, which is classified as ametalloid, is not found naturally on Earth.
Elemental boron is used as a dopant in the semiconductorindustry.
Natural boron is composed of two stable isotopes, one of which (boron-10) has a number of uses
as a neutron-capturing agent.
Elemental boron is rare and poorly studied because the material is extremely difficult to prepare.
Chemically, boron behaves more similarly to silicon than to aluminium.
TERMS [ edit ]
Boron
A chemical element with chemical symbol B and atomic number5.
borate
A salt formed by the combination of boric acid with a base or positive radical.
metalloid
A chemical element with properties in between those of nonmetals and metals.
spallation
A type of nuclear fission reaction in which cosmic rays of light cause a nucleus to emit a large
number of nucleons (protons and neutrons), leading to the formation of new elements
(nucleosynthesis).
Give us feedback on this content: FULL TEXT [edit ]
Boron is a chemical element with the
chemical symbol B and atomic number 5.
Boron is produced entirely by cosmic
ray spallation (as a result of nuclear
reactions), and not by stellar
nucleosynthesis (not within stars as a
result of fusionor supernovae). As a result,
it is a low-abundance element in both the
solar system and the Earth's crust. Natural
boron is composed of two stable
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isotopes: 11B is more abundant than 10B, which has a number of uses as a neutron-capturing
agent. Several allotropes of boron exist. Amorphous boron is a brown powder,
while crystalline boron is black, extremely hard (about 9.5 on the Mohs scale), and a
poor conductor at roomtemperature. Elemental boron is used as a dopant in the
semiconductor industry.
Chemical Properties of Boron
Elemental boron is rare and poorly studied because the material is extremely difficult to
prepare. Most studies on "boron" involve samples that contain small amounts of carbon.
Chemically, boron behaves more similarly to silicon than toaluminum. Crystalline boron is
chemically inert and resistant to attack from boiling hydrofluoric or hydrochloric acid. When
finely divided, it can be attacked slowly by hot, concentrated hydrogen peroxide or nitric acid;
hot sulfuric acid; or a hotmixture of sulfuric and chromic acids.
On Earth, boron is concentrated by the water-solubility of its more common naturallyoccurring compounds, the borateminerals. These are mined industrially as evaporites, such
as borax and kernite. Chemically uncombined boron, which is classified as a metalloid,
is not found naturally on Earth. Industrially, very pure boron can be produced, but this is
difficult, because boron tends to form refractory materials that contain small amounts of
carbon or other elements.
Boron
Boron has a black­brown appearance.
Biological Significance of Boron
Boron is essential to life, although its exact physiological role in animals is not wellestablished. Small amounts of boron compounds play a role strengthening the cell walls of all
plants, thus making boron necessary in soils. Experiments indicate a role for boron as an
ultratrace element in animals. Deficiency of boron in rats has been shown to result in poor
coat or hair quality.
Borates have low toxicity for mammals (similar to table salt), but are more toxic to
arthropods and have been used as insecticides. Boric acid is mildly antimicrobial, and a
natural, boron-containing, organic antibiotic does exist.
Some signaling compounds of boron which are used for bacterial cell to cell communication
(known as "quorum sensing") have been discovered recently. This signaling system is used as
a response to the local population density of bacterial cells, and mediates processes such as
biofilm formation, virulence, and antibiotic resistance. A known example of a boroncontaining quorum sensing signaling molecule is Autoinducer-2 (AI-2).
Autoinducer-2
Autoinducer­2 (AI­2) is one of the few known biomolecules containing the element Boron. AI­2 is used by
many types of bacteria as a signaling molecule mediating quorum sensing.