Boron
General:
Name: Boron
Type: Metalloid
Density @ 293 K: 2.34 g/cm3
Type: Metalloid
Density @ 293 K: 2.34 g/cm3
Symbol: B
Atomic weight: 10.81
Atomic volume: 4.6 cm3/mol
Atomic weight: 10.81
Atomic volume: 4.6 cm3/mol
States
State (s, l, g): solid
Melting point: 2348 K (2075 oC)
Melting point: 2348 K (2075 oC)
Boiling point: 4000 K (3727 oC)
Appearance
Structure: rhombohedral; B12 is icosahedral.
Hardness: 9.3 mohs
Hardness: 9.3 mohs
Color: black
Harmful effects:
Elemental boron is not known to be toxic.
Reactions & Compounds
Reaction with air: mild, w/ht ⇒ B2O3
Reaction with 15 M HNO3: none
Oxide(s): B2O3
Hydride(s): B2H6 and many BxHy
Reaction with 15 M HNO3: none
Oxide(s): B2O3
Hydride(s): B2H6 and many BxHy
Reaction with 6 M HCl: none
Reaction with 6 M NaOH: none
Chloride(s): BCl3 and many BxCly
Reaction with 6 M NaOH: none
Chloride(s): BCl3 and many BxCly
Radius
Atomic radius: 85 pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (1+ ion): pm
Ionic radius (3+ ion): 41 pm
Ionic radius (1- ion): pm
Ionic radius (3+ ion): 41 pm
Ionic radius (1- ion): pm
Conductivity
Thermal conductivity: 27.4 W m-1 K-1
Electrical conductivity: 5.0 x10-4 S cm-1
Energies
Specific heat capacity: 1.02 J g-1 K-1
Heat of fusion: 50.2 kJ mol-1
1st ionization energy: 800.6 kJ mol-1
3rd ionization energy: 3659.7 kJ mol-1
Heat of fusion: 50.2 kJ mol-1
1st ionization energy: 800.6 kJ mol-1
3rd ionization energy: 3659.7 kJ mol-1
Heat of atomization: 563 kJ mol-1
Heat of vaporization: 480 kJ mol-1
2nd ionization energy: 2427.1 kJ mol-1
Electron affinity: 26.7 kJ mol-1
Heat of vaporization: 480 kJ mol-1
2nd ionization energy: 2427.1 kJ mol-1
Electron affinity: 26.7 kJ mol-1
Oxidation & Electrons
Shells: 2,3
Minimum oxidation number: 0
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 2.04
Minimum oxidation number: 0
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 2.04
Electron configuration: 1s2 2s2 2p1
Maximum oxidation number: 3
Max. common oxidation no.: 3
Polarizability volume: 3 Å3
Maximum oxidation number: 3
Max. common oxidation no.: 3
Polarizability volume: 3 Å3
Characteristics:
Boron is a metalloid, intermediate between metals and non-metals. It exists in many polymorphs (different crystal lattice structures), some more metallic than others. Metallic boron is extremely hard and has a very high melting point.
Boron does not generally make ionic bonds, it forms stable covalent bonds.
Boron can transmit portions of infrared light.
Boron is a poor room temperature conductor of electricity but its conductivity improves markedly at higher temperatures.
Boron is a metalloid, intermediate between metals and non-metals. It exists in many polymorphs (different crystal lattice structures), some more metallic than others. Metallic boron is extremely hard and has a very high melting point.
Boron does not generally make ionic bonds, it forms stable covalent bonds.
Boron can transmit portions of infrared light.
Boron is a poor room temperature conductor of electricity but its conductivity improves markedly at higher temperatures.
Uses:
Boron is used to dope silicon and germanium semiconductors, modifying their electrical properties.
Boron oxide (B2O3) is used in glassmaking and ceramics.
Borax (Na2B4O7.10H2O) is used in making fiberglass, as a cleansing fluid, a water softener, insecticide, herbicide and disinfectant.
Boric acid (H3BO3) is used as a mild antiseptic and as a flame retardant.
Boron Nitride's hardness is second only to diamond, but it has better thermal and chemical stability, hence boron nitride ceramics are used in high-temperature equipment.
Boron nitride nanotubes can have a similar structure to carbon nanotubes. BN nanotubes are more thermally and chemically stable than carbon nanotubes and, unlike carbon nanotubes, boron nitride nanotubes are electrical insulators.
Boron carbide (B4C) is used in tank armor and bullet proof vests.
Abundance & Isotopes
Abundance earth's crust: 10 parts per milllion by weight, 1 part per million by moles
Abundance solar system: 2 parts per billion by weight, 0.2 parts per billion by moles
Cost, pure: $1114 per 100g
Cost, bulk: $500 per 100g
Source: Boron compunds are usually is found in sediments and sedimentary rock formations. The chief sources of boron are Na2B4O6(OH)2.3H2O - known as rasorite or kernite; borax ore (known as tincal); and with calcium in colemanite (CaB3O4(OH)4.H2O). Boron also occurs as orthoboric acid in some volcanic spring waters.
Isotopes: 11 whose half-lives are known, with mass numbers 7 to 17. Of these, two are stable: 10B and 11B. 10B is used in nuclear reactors as a neutron-capturing substance.
Abundance solar system: 2 parts per billion by weight, 0.2 parts per billion by moles
Cost, pure: $1114 per 100g
Cost, bulk: $500 per 100g
Source: Boron compunds are usually is found in sediments and sedimentary rock formations. The chief sources of boron are Na2B4O6(OH)2.3H2O - known as rasorite or kernite; borax ore (known as tincal); and with calcium in colemanite (CaB3O4(OH)4.H2O). Boron also occurs as orthoboric acid in some volcanic spring waters.
Isotopes: 11 whose half-lives are known, with mass numbers 7 to 17. Of these, two are stable: 10B and 11B. 10B is used in nuclear reactors as a neutron-capturing substance.
Discovery of boron
The boron compounds such as borax (sodium tetraborate, Na2B4O7·10H2O) were known and used by ancient cultures for thousands of years. Borax name comes from the Arabic Buraq, which means "white."
Boron was first isolated in 1808 in part by the French chemists Joseph L. Gay-Lussac and Thenard LJ and independently by Sir Humphry Davy in London. Gay-Lussac and Thenard reacted boric acid with magnesium or sodium boron to give a gray solid. They believed that it shares characteristics with the sulfur and phosphorus and the name he bore.
Davy first tried to produce boron by electrolysis of boric acid, but was not satisfied with the results. He had more success reacting boric acid with potassium in a hydrogen atmosphere. The result was a powdery substance.
Davy said the substance was "the darkest shades of olive. It is opaque, very brittle, and the powder does not scratch the glass." After making a number of chemical reactions to verify the uniqueness of the substance, Davy wrote, "there are strong reasons to consider the basis of boric acid as a metal in nature, and I venture to propose for boracium name. "
Neither party had, in fact, a product of pure boron. Their samples were only about 60% pure. In 1909 William Weintraub was able to produce 99% pure boron, reducing boron halides with hydrogen.
Almost a century later, in 2004, Jiuhua Chen and Vladimir L. Solozhenko produced a new form of boron, but uncertain of its structure.
In 2009, a team led by Artem Oganov was able to show the new form of boron has two structures, icosohedra B12 and B2 pairs. Gamma-bore, as it was called, is almost as hard as diamond and more resistant to heat than the diamond.
Speaking of metal part of the boron, non-metallic element properties, Oganov said, "Boron is a truly schizophrenic. Is an element of total frustration. He does not know what to do. The result is something terribly complicated. "
The boron compounds such as borax (sodium tetraborate, Na2B4O7·10H2O) were known and used by ancient cultures for thousands of years. Borax name comes from the Arabic Buraq, which means "white."
Boron was first isolated in 1808 in part by the French chemists Joseph L. Gay-Lussac and Thenard LJ and independently by Sir Humphry Davy in London. Gay-Lussac and Thenard reacted boric acid with magnesium or sodium boron to give a gray solid. They believed that it shares characteristics with the sulfur and phosphorus and the name he bore.
Davy first tried to produce boron by electrolysis of boric acid, but was not satisfied with the results. He had more success reacting boric acid with potassium in a hydrogen atmosphere. The result was a powdery substance.
Davy said the substance was "the darkest shades of olive. It is opaque, very brittle, and the powder does not scratch the glass." After making a number of chemical reactions to verify the uniqueness of the substance, Davy wrote, "there are strong reasons to consider the basis of boric acid as a metal in nature, and I venture to propose for boracium name. "
Neither party had, in fact, a product of pure boron. Their samples were only about 60% pure. In 1909 William Weintraub was able to produce 99% pure boron, reducing boron halides with hydrogen.
Almost a century later, in 2004, Jiuhua Chen and Vladimir L. Solozhenko produced a new form of boron, but uncertain of its structure.
In 2009, a team led by Artem Oganov was able to show the new form of boron has two structures, icosohedra B12 and B2 pairs. Gamma-bore, as it was called, is almost as hard as diamond and more resistant to heat than the diamond.
Speaking of metal part of the boron, non-metallic element properties, Oganov said, "Boron is a truly schizophrenic. Is an element of total frustration. He does not know what to do. The result is something terribly complicated. "
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