BORON
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BORON |
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Introduction |
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| Atomic Number: | 5 | Group: | 13 or III A | 5 | 10.811 |
| Average Atomic Mass: | 10.811 | Period: | 2 |
B |
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CAS Number: |
7440-42-8 | ||||
| Boron | |||||
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Classification |
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| Metal | Nonmetal | Metalloid | ||
| Alkali Metal | Alkali Earth Metal | Transition Metal | Chalcogen | Halogen |
| Noble Gas | Lanthanoid | Actinoid |
Rare Earth Metal |
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| Transuranium | No Stable Isotopes | |||
| Solid | Liquid | Gas |
Assumed Solid |
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Description |
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| Boron compounds have been known for thousands of years, but the element was not discovered until 1808 by Sir Humphry Davy and by Gay-Lussac and Thenard. The element is not found free in nature, but occurs as orthoboric acid usually in certain volcanic spring waters and as borates in borax and colemanite. Ulexite, another boron mineral, is interesting as it is nature’s own version of “fiber optics.” Important sources of boron are the ores rasorite (kernite) and tincal (borax ore). Both of these ores are found in the Mojave Desert. Tincal is the most important source of boron from the Mojave. Extensive borax deposits are also found in Turkey. Boron exists naturally as 19.9% 10B isotope and 80.1% 11B isotope. Eleven isotopes of boron are known. High-purity crystalline boron may be prepared by the vapor phase reduction of boron trichloride or tribromide with hydrogen on electrically heated filaments. The impure, or amorphous, boron, a brownish-black powder, can be obtained by heating the trioxide with magnesium powder. Boron of 99.9999% purity has been produced and is available commercially. Elemental boron has an energy band gap of 1.50 to 1.56 eV, which is higher than that of either silicon or germanium. It has interesting optical characteristics, transmitting portions of the infrared, and is a poor conductor of electricity at room temperature, but a good conductor at high temperature. Amorphous boron is used in pyrotechnic flares to provide a distinctive green color, and in rockets as an igniter. By far the most commercially important boron compound in terms of dollar sales is Na2B4O7 · 5H2O. This pentahydrate is used in very large quantities in the manufacture of insulation fiberglass and sodium perborate bleach. Boric acid is also an important boron compound with major markets in textile fiberglass and in cellulose insulation as a flame retardant. Next in order of importance is borax (Na2B4O7 · 10H2O) which is used principally in laundry products. Use of borax as a mild antiseptic is minor in terms of dollars and tons. Boron compounds are also extensively used in the manufacture of borosilicate glasses. Other boron compounds show promise in treating arthritis. The isotope boron-10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons. Boron nitride has remarkable properties and can be used to make a material as hard as diamond. The nitride also behaves like an electrical insulator but conducts heat like a metal. It also has lubricating properties similar to graphite. The hydrides are easily oxidized with considerable energy liberation, and have been studied for use as rocket fuels. Demand is increasing for boron filaments, a high-strength, lightweight material chiefly employed for advanced aerospace structures. Boron is similar to carbon in that it has a capacity to form stable covalently bonded molecular networks. Carboranes, metalloboranes, phosphacarboranes, and other families comprise thousands of compounds. Crystalline boron (99%) costs about $8/g. Amorphous boron costs about $4/g. Elemental boron and the borates are not considered to be toxic, and they do not require special care in handling. However, some of the more exotic boron hydrogen compounds are definitely toxic and do require care. 1 |
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Physical Properties |
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| Normal Melting Point: | 2075 °C = 2348.15 K = 3767 °F 2 | Normal Boiling Point: | 4000 °C = 4273.15 K = 7232 °F 2 |
| Sublimation Point: | Triple Point: | ||
| Critical Point: | |||
| Density: | 2.34 g/cm3 | Crystal Structure: | rhombohedral |
| Atomic Radius: | 1.17 Ǻ = 117 pm | Covalent Radius: | 0.82 Ǻ = 82 pm |
| Ionic Radius: | 0 Ǻ = 0 pm | Atomic Volume: | 4.6 cm3/mol |
| Qualitative Solubility: | v slightly s HNO3 3 | ||
| Note: Unless otherwise stated, solubility is for water at 25 degrees Celsius. | |||
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Electron Configuration and Bonding |
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| Predicted Electron Configuration: | [He] 2s2 2p1 |
Lewis Dot Diagram |
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| Actual Electron Configuration: | [He] 2s2 2p1 |
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| Block: | p | B |
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| Highest Occupied Energy Level: | 2 | |||||||
| Valence Electrons: | 3 |
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| Quantum Numbers: | n = 2 | ℓ = 1 | mℓ = -1 | ms = +½ | ||||
| Please note that information in this section can be derived entirely from the periodic table. Although most people do not discuss valence electrons of the d-block and f-block elements, on this page the number of electrons in the highest energy level of the actual electron configuration was used to determine valence electrons. | ||||||||
| Electronegativity (Pauling): | 2.04 | Electropositivity (Pauling): | 1.96 | ||||
| Electron Affinity: | 0.28 eV = 27.02 kJ/mol = 6.46 kcal/mol | Oxidation States: | +3 | ||||
| Work Function:4 | 4.75 eV = 7.6095E-19 J | ||||||
| Ionization Potential 5 | eV | kJ/mol | Ionization Potential 5 | eV | kJ/mol | ||
| 1 | 8.29803 | 800.6 | 4 | 259.37521 | 25025.9 | ||
| 2 | 25.15484 | 2427.1 | 5 | 340.2258 | 32826.8 | ||
| 3 | 37.93064 | 3659.7 | |||||
| Note: Only the electronvolt values are given in the CRC Handbook, a conversion factor was used to find the kJ/mol value. | |||||||
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Thermochemistry |
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| Specific Heat: | 1.02 J/g°C = 0.244 cal/g°C | Thermal Conductivity: | 27 (W/m)/K, 27ºC | ||||
| Heat of Fusion: | 50.2 kJ/mol = 4643.4 J/g | Heat of Vaporization: | 489.7 kJ/mol = 45296.5 J/g | ||||
| State of Matter | Enthalpy of Formation | Entropy of Formation | Gibbs Free Energy | ||||
| (kcal/mol) | (kJ/mol) | (cal/K) | (J/K) | (kcal/mol) | (kJ/mol) | ||
| (s) | 0 | 0 | 1.40 | 5.8576 | 0 | 0 | |
| (g) | 134.5 | 562.748 | 36.65 | 153.3436 | 124.0 | 518.816 | |
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Video |
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| Video on boron from the University of Nottingham's periodicvideos.com | |
| Flame tests: sodium, copper, boron, potassium, lead, and lithium. | |
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Isotopes |
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| Nuclide | Mass | Half-Life | Nuclear Spin | Binding Energy (kJ/mol) |
| 6B | 6.04681(75)# | -71233830.3366486 | ||
| 7B | 7.02992(8) | 350(50)E-24 s [1.4(2) MeV] | (3/2-) | 2227170023.64664 |
| 8B | 8.0246072(11) | 770(3) ms | 2+ | 3482951526.08516 |
| 9B | 9.0133288(11) | 800(300)E-21 s [0.54(21) keV] | 3/2- | 5278020451.7365 |
| 10B | 10.0129370(4) | STABLE | 3+ | 6174277005.36641 |
| 11B | 11.0093054(4) | STABLE | 3/2- | 7223331662.24004 |
| 12B | 12.0143521(15) | 20.20(2) ms | 1+ | 7553336421.49677 |
| 13B | 13.0177802(12) | 17.33(17) ms | 3/2- | 8063103655.15741 |
| 14B | 14.025404(23) | 12.5(5) ms | 2- | 8123464702.80749 |
| 15B | 15.031103(24) | 9.87(7) ms | 3/2- | 8363588224.86179 |
| 16B | 16.03981(6) | <190E-12 s [<0.1 MeV] | 0- | 8423949272.51202 |
| 17B | 17.04699(18) | 5.08(5) ms | (3/2-) | 8574191557.36437 |
| 18B | 18.05617(86)# | <26 ns | (4-)# | 8454790130.61022 |
| 19B | 19.06373(43)# | 2.92(13) ms | (3/2-)# | 8605032415.46256 |
| Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 6 | ||||
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Reactions |
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| As elemental boron burns in oxygen, diboron trioxide is produced. |
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Abundance |
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| Earth: | Source Compounds: | oxides 7 |
| Earth: | Ocean Water: | 4.44 mg/L 8 |
| Earth: | Crust: | 10 mg/kg = 0.001% 8 |
| Earth: | Total: | 9.6 ppb 9 |
| Mercury: | Total: | 0.11 ppb 9 |
| Venus: | Total: | 10.0 ppb 9 |
| Human Body: | Total: | 0.00007% 10 |
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Compounds |
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Safety |
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| Note: Not every link below has an entry for every element on the periodic table. Sites were selected based on those that had a large number of element and compound entries. |
| Scorecard's Pollution Information − not an MSDS, but it does provide basic information (among other things) on human heath hazards and industrial uses. |
| Although not truly an MSDS, Oxford University's Physical and Theoretical Chemistry Laboratory does provide some basic information. |
| Iowa State University |
| ESPI Metals |
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Languages |
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| Afrikaans: | Boor | Albanian: | Bor | Armenian: | Բոր | Arabic: | بورون |
| Aromanian: | Boru | Basque: | Boroa | Bosnian: | Bor | Breton: | Bor |
| Bulgarian: | Бор | Byelorussian: | Бор | Catalan: | Bor | Chinese: | 硼 |
| Cornish: | Boron | Croatian: | Bor | Czech: | Bor | Danish: | Bor |
| Dutch: | Boor | Esperanto: | Borio | Estonian: | Boor | Faroese: | Bor |
| Finnish: | Boori | French: | Bore | Friulian: | Bôr | Frisian: | Boar |
| Galician: | Boro | Georgian: | ბორი | German: | Bor | Greek: | Βοριο |
| Hebrew: | בור | Hungarian: | Bór | Icelandic: | Bór | Irish Gaelic: | Bórón |
| Italian: | Boro | Japanese: | ホウ素 | Kashubian: | Bòr | Kazakh: | Бор |
| Korean: | 붕소 | Latvian: | Bors | Lithuanian: | Boras | Luxembourgish: | Bor |
| Macedonian: | Бор | Malay: | Boron | Maltese: | Boron | Manx Gaelic: | Boron |
| Mokshan: | Бора | Mongolian: | Бор | Norwegian: | Bor | Occitan: | Bòr |
| Ossetian: | Бор | Polish: | Bor | Portuguese: | Boro | Russian: | Бор |
| Scottish Gaelic: | Bòron | Serbian: | Бор | Slovak: | Bór | Spanish: | Boro |
| Sudovian: | Baras | Swahili: | Boroni | Swedish: | Bor | Tajik: | Bor |
| Thai: | โบรอน | Turkish: | Bor | Ukranian: | Бор | Uzbek: | Бор |
| Vietnamese: | Bo | Welsh: | Boron |
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For More Information |
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Sources |
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| (1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4-6. |
| (2) - Lide, David R. CRC Handbook; CRC Press: Boca Raton, FL, 2002; p 4-132. |
| (3) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4-8 - 4-149. |
| (4) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1-132. |
| (5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10-178 - 10-180. |
| (6) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009). |
| (7) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 965. |
| (8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14-17. |
| (9) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 962. |
| (10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 7-17. |
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BORON |
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| Site designed and maintained by Mr. Everett. |
| Last update: Thursday, August 12, 2010 |