Boron

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Boron
5B
-

B

Al
berylliumboroncarbon
Appearance
black-broun
General properties
Name, seembol, nummer boron, B, 5
Pronunciation /ˈbɔərɒn/
Element category metalloid
Group, period, block 13, 2, p
Staundart atomic wicht 10.81(1)
Electron confeeguration [He] 2s2 2p1
2, 3
Electron shells of boron (2, 3)
History
Discovery Joseph Louis Gay-Lussac an Louis Jacques Thénard[1] (30 June 1808)
First isolation Humphry Davy[2] (9 Julie 1808)
Physical properties
Phase solid
Liquid density at m.p. 2.08 g·cm−3
Meltin pynt 2349 K, 2076 °C, 3769 °F
Boilin pynt 4200 K, 3927 °C, 7101 °F
Heat o fusion 50.2 kJ·mol−1
Heat o vaporization 480 kJ·mol−1
Molar heat capacity 11.087 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2348 2562 2822 3141 3545 4072
Atomic properties
Oxidation states 3, 2, 1[3]
(mildly acidic oxide)
Electronegativity 2.04 (Pauling scale)
Ionization energies
(more)
1st: 800.6 kJ·mol−1
2nt: 2427.1 kJ·mol−1
3rd: 3659.7 kJ·mol−1
Atomic radius 90 pm
Covalent radius 84±3 pm
Van der Waals radius 192 pm
Miscellanea
Crystal structure rhombohedral
Boron has a rhombohedral crystal structure
Magnetic orderin diamagnetic[4]
Electrical resistivity (20 °C) ~106 Ω·m
Thermal conductivity 27.4 W·m−1·K−1
Thermal expansion (25 °C) (β form) 5–7[5] µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 16,200 m·s−1
Mohs hairdness ~9.5
CAS registry nummer 7440-42-8
Most stable isotopes
Main article: Isotopes o boron
iso NA hauf-life DM DE (MeV) DP
10B 19.9(7)% 10B is stable wi 5 neutrons[6]
11B 80.1(7)% 11B is stable wi 6 neutrons[6]
10B content may be as low as 19.1% and as high as 20.3% in natural samples. 11B is the remainder in such cases.[7]
· r

Boron is a chemical element wi seembol B an atomic nummer 5. Acause boron is produced entirely bi cosmic ray spallation an nae bi stellar nucleosynthesis,[8] it is a law-abundance element in baith the solar seestem an the Yird's crust. Boron is concentratit on Yird bi the watter-solubility o its mair common naiturally occurrin compoonds, the borate minerals. These are mined industrially as evaporites, such as borax an kernite.

References[eedit | eedit soorce]

  1. Gay Lussac, J.L. and Thenard, L.J. (1808) "Sur la décomposition et la recomposition de l'acide boracique," Annales de chimie [later: Annales de chemie et de physique], vol. 68, pp. 169–174.
  2. Davy H (1809). "An account of some new analytical researches on the nature of certain bodies, particularly the alkalies, phosphorus, sulphur, carbonaceous matter, and the acids hitherto undecomposed: with some general observations on chemical theory". Philosophical Transactions of the Royal Society of London 99: 33–104. 
  3. Zhang, K.Q.; Guo, B.; Braun, V.; Dulick, M.; Bernath, P.F. (1995). "Infrared Emission Spectroscopy of BF and AIF". J. Molecular Spectroscopy 170: 82. Bibcode:1995JMoSp.170...82Z. doi:10.1006/jmsp.1995.1058. 
  4. Lide, David R. (ed.) (2000). Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics. CRC press. ISBN 0849304814. 
  5. Holcombe Jr., C. E.; Smith, D. D.; Lorc, J. D.; Duerlesen, W. K.; Carpenter; D. A. (October 1973). "Physical-Chemical Properties of beta-Rhombohedral Boron". High Temp. Sci. 5 (5): 349–57. 
  6. 6.0 6.1 "Atomic Weights and Isotopic Compositions for All Elements". National Institute of Standards and Technology. Retrieved 2008-09-21. 
  7. Szegedi, S.; Váradi, M.; Buczkó, Cs. M.; Várnagy, M.; Sztaricskai, T. (1990). "Determination of boron in glass by neutron transmission method". Journal of Radioanalytical and Nuclear Chemistry Letters 146 (3): 177. doi:10.1007/BF02165219. 
  8. "Q & A: Where does the element Boron come from?". physics.illinois.edu. Retrieved 2011-12-04.