Template:Infobox boron

Boron,  5B
Template:Infobox element/symbol-to-top-image-alt
General properties
PronunciationTemplate:Infobox element/pronunciation
Allotropesα-, β-rhombohedral, β-tetragonal (and more)
Appearanceblack-brown
Standard atomic weight (Ar, standard)Template:Infobox element/standard atomic weight
Mass numberTemplate:Infobox element/symbol-to-most-stable-isotope (most stable isotope)
Boron in the periodic table
Template:Infobox element/periodic table
Atomic number (Z)5
GroupTemplate:Infobox element/group
Periodperiod 2
Blockp-block
Element categoryTemplate:Infobox element/category format
Electron configuration[He] 2s2 2p1
Electrons per shell
2, 3
Physical properties
Phase at STPsolid
Melting point2349 K ​(2076 °C, ​3769 °F)
Boiling point4200 K ​(3927 °C, ​7101 °F)
Density when liquid (at m.p.)2.08 g/cm3
Heat of fusion50.2 kJ/mol
[[Enthalpy of vaporization|Heat of Template:Engvar]]508 kJ/mol
Molar heat capacity11.087 J/(mol·K)
[[Vapor pressure|Template:Engvar pressure]]
Atomic properties
Oxidation statesTemplate:Infobox element/symbol-to-oxidation-state
ElectronegativityPauling scale: 2.04
[[Ionization energy|Template:Engvar energies]]
  • 1st: 800.6 kJ/mol
  • 2nd: 2427.1 kJ/mol
  • 3rd: 3659.7 kJ/mol
  • (more)
Atomic radiusempirical: 90 pm
Covalent radius84±3 pm
Van der Waals radius192 pm
Template:Infobox element/spectral lines
Other properties
Crystal structureTemplate:Infobox element/crystal structure
Speed of sound thin rod16,200 m/s (at 20 °C)
Thermal expansionβ form: 5–7 µm/(m·K) (at 25 °C)[1]
Thermal conductivity27.4 W/(m·K)
Electrical resistivity~106 Ω·m (at 20 °C)
Magnetic orderingdiamagnetic[2]
Magnetic susceptibility−6.7·10−6 cm3/mol[3]
Mohs hardness~9.5
CAS Number7440-42-8
History
DiscoveryJoseph Louis Gay-Lussac and Louis Jacques Thénard[4] (30 June 1808)
First isolationHumphry Davy[5] (9 July 1808)
Main isotopes of boron
Template:Infobox element/isotopes table
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.[6]
| references

Template:Infobox element/element navigation Template:Template reference list Five of these are named references. They may be cited in the containing article as

  • <ref name="v1" /> for the source Infrared Emission Spectroscopy of BF and AIF
  • <ref name="magnet" /> for the source from Handbook of Chemistry and Physics
  • <ref name="NISTic" /> for the source Atomic Weights and Isotopic Compositions for All Elements
  • <ref name="Lussac" /> for the source by Gay-Lussac
  • <ref name="Davy" /> for the source by Davy

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  1. 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.
  2. Lide, David R. (ed.) (2000). Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics (PDF). CRC press. ISBN 0849304814.CS1 maint: Extra text: authors list (link)
  3. Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  4. Gay Lussac, J.L. & Thenard, L.J. (1808). "Sur la décomposition et la recomposition de l'acide boracique". Annales de chimie. 68: 169–174.
  5. 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: 39–104. doi:10.1098/rstl.1809.0005.
  6. 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.
  7. Zhang, K.Q.; Guo, B.; Braun, V.; Dulick, M.; Bernath, P.F. (1995). "Infrared Emission Spectroscopy of BF and AIF" (PDF). J. Molecular Spectroscopy. 170: 82. Bibcode:1995JMoSp.170...82Z. doi:10.1006/jmsp.1995.1058.
  8. Template:Cite article
  9. 9.0 9.1 "Atomic Weights and Isotopic Compositions for All Elements". National Institute of Standards and Technology. Retrieved 2008-09-21.