Boron

(noun)

A chemical element with chemical symbol B and atomic number 5.

Related Terms

Examples of Boron in the following topics:

  • Borates: Boron-Oxygen Compounds

    • Borates are the name for a large number of boron-containing oxoanions.
    • Boron monoxide (B2O) is another chemical compound of boron and oxygen.
    • Boron trioxide (or diboron trioxide) is one of the oxides of boron.
    • Boron suboxide (chemical formula B6O) is a solid compound containing six boron atoms and one oxygen atom.
    • B6O can be synthesized by reducing B2O3 with boron or by oxidation of boron with zinc oxide or other oxidants.

  • Elemental Boron

    • Boron is a chemical element with the chemical symbol B and atomic number 5.
    • 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 room temperature.
    • Elemental boron is used as a dopant in the semiconductor industry.
    • Small amounts of boron compounds play a role strengthening the cell walls of all plants, thus making boron necessary in soils.

  • Trihalides: Boron-Halogen Compounds

    • Boron tribromide (BBr3) is a colorless, fuming liquid compound that contains boron and bromine.
    • The reaction of boron carbide with bromine at temperatures above 300 °C leads to the formation of boron tribromide.
    • Boron trichloride is produced industrially by direct chlorination of boron oxide and carbon at 500 °C.
    • Boron trichloride is a starting material for the production of elemental boron.
    • Boron (III) trifluoride structure, BF3, showing the "empty" boron p orbital in pi-type coordinate covalent bonds.

  • The Incomplete Octet

    • Boron and aluminum, from Group III (or 13), display different bonding behavior than previously discussed.
    • Consider boron trifluoride (BF3).
    • We might conclude from this one example that boron atoms obey a sextet rule.
    • However, boron will form a stable ion with hydrogen, BH4-, in which the boron atom does have a complete octet.
    • This covalent compound (NH3BF3) shows that boron can have an octet of electrons in its valence level.

  • Boranes: Boron-Hydrogen Compounds

    • Boranes are chemical compounds of boron and hydrogen with general formula BxHy; many readily oxidize on contact with air.
    • Boranes are chemical compounds of boron and hydrogen.
    • The larger boranes all consist of boron clusters that are polyhedral, some of which exist as isomers.
    • The development of the chemistry of boron hydrides led to new experimental techniques and theoretical concepts.
    • Boron hydrides have been studied as potential fuels, for rockets, and for automotive uses.

  • sp2 Hybridization

    • Boron trifluoride (BF3) has a boron atom with three outer-shell electrons in its normal or ground state, as well as three fluorine atoms, each with seven outer electrons.
    • One of the three boron electrons is unpaired in the ground state.
    • One of the three boron electrons is unpaired in its ground state.
    • The atomic s- and p-orbitals in boron's outer shell mix to form three equivalent hybrid orbitals.

  • Covalent Crystals

    • Cubic boron nitride is the second-hardest material after diamond, and it is used in industrial abrasives and cutting tools.
    • Recent interest in boron nitride has centered on its carbon-like ability to form nanotubes and related nanostructures.
    • Hexagonal boron nitride, a two-dimensional material, is similar in structure to graphite.
    • Cubic boron nitride adopts a crystal structure, which can be constructed by replacing every two carbon atoms in diamond with one boron atom and one nitrogen atom.
    • Cubic boron nitride is the second-hardest material, after diamond.

  • Addition of Lewis Acids (Electrophilic Reagents)

    • Mercury and boron are removed from the organic substrate in the second step of oxymercuration and hydroboration respectively.
    • Addition of hydroperoxide anion to the electrophilic borane generates a tetra-coordinate boron peroxide, having the general formula R3B-O-OH(-).
    • This undergoes successive intramolecular shifts of alkyl groups from boron to oxygen, accompanied in each event by additional peroxide addition to electron deficient boron.
    • Boron and hydrogen have rather similar electronegativities, with hydrogen being slightly greater, so it is not likely there is significant dipolar character to the B-H bond.
    • As shown in the following equation, this bonding might generate a dipolar intermediate consisting of a negatively-charged boron and a carbocation.

  • Hydroboration Reactions and Oxidations

    • As with alkenes, the B-H reagent group adds in an apparently anti-Markovnikov manner, due to the fact that the boron is the electrophile, not the hydrogen.
    • Further addition to the resulting boron-substituted alkene does not occur, and the usual oxidative removal of boron by alkaline hydrogen peroxide gives an enol which rapidly rearranges to the aldehyde tautomer.

  • Carbides

    • Covalent carbides are found in carbides of silicon and boron.
    • Boron carbide (B4C), on the other hand, has an unusual structure that includes icosahedral boron units linked by carbon atoms.
    • In this respect, boron carbide is similar to the boron-rich borides.
    • Both silicon carbide (also known as carborundum) and boron carbide are very hard and refractory materials.