Periodic Table of the Elements
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Bottom FACULTY OF CHEMICAL TECHNOLOGY o PERIODIC TABLE OF THE ELEMENTS Bottom
  A B C D E F G H I J K L M N O P R S T U V X Z  
Periodic Table of the Elements Tableau périodique des éléments Periodni sustav elemenata Tavola periodica degli elementi Das Periodensystem der Elemente
Boron Bore Bor Boro Bor

 
Atomic number: 5
Group numbers: 13
Period: 2
 
Discovery date: 1808
B

Bor
NEIGHBOURS

 
 
 
4
Be
 5
B
 6
C
12
Mg
 13
Al
 14
Si


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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 (England) and independently by Joseph-Louis Gay-Lussac (France) and L. J. Thenard (France). The origin of the name comes from the Arabic word buraq and the Persian word burah meaning boraks (Na2B4O7×10H2O). It is hard, brittle, lustrous black semimetal. Unreactive with oxygen, water, alkalis or acids. Combines with most metals to form borides.
Bottom BORON GROUP Top

Relative atomic mass: 10.811(7) Electronic configuration: [He] 2s2 2p1
Formal oxidation number: +3 Electronegativities: 2.04
Thermal conductivity: 27 W m-1 K-1 Electrical resistivity (20 °C): 1.8E+12 μΩcm
Atomic radius: 79.5 pm Standard state (20 °C): solid
Density (g dm-3): 2340 (beta, 293 K) Molar volume (cm3 mol-1): 4.62 (beta, 293 K)


Bottom THERMAL PROPERTIES Top

Melting point: 2075 °C Heat of fusion: 22.2 kJ mol-1
Boiling point: 4000 °C Heat of vaporization: 504.5 kJ mol-1
Critical temperature: 3011 °C Heat of atomization: 557.64 kJ mol-1


Bottom IONIZATION ENERGIES AND ABUNDANCE Top

1st ionization energy: 800.64 kJ mol-1 Abundance of element (air): - ppm
2nd ionization energy: 2427.09 kJ mol-1 Abundance of element (Earth's crust): 10 ppm
3rd ionization energy: 3659.78 kJ mol-1 Abundance of element (oceans): 4.8 ppm


Bottom ISOTOPES Top

Isotopes Relative atomic mass Abundance (%)
10B10.0129370(3)19.9(2)
11B11.0093055(5)80.1(2)


Bottom MINERALS AND USES Top

Boron is obtained from kernite, a kind of borax (Na2B4O7.10H2O). High purity boron is produced by electrolysis of molten potassium fluroborate and potassium chloride (KCl). Amorphous boron is used in pyrotechnic flares to provide a distinctive green color and in rockets as an igniter. The price of 99.5 % pure boron pieces is 997.90 € for 250 g.

Bottom REDUCTION POTENTIALS Top

Balanced half-reaction   Eo / V      Annotation
H3BO3 + 3H+ + 3e- = B(s) + 3H2O - 0.869  
H2BO3- + 4H+ + 3e- = B(s) + 3H2O - 0.687  
HBO32- + 5H+ + 3e- = B(s) + 3H2O - 0.437  
BO33- + 6H+ + 3e- = B(s) + 3H2O - 0.165  
B(OH)3 + 3H+ + 3e- = B(s) + 3H2O - 0.87  
BF4- + 3e- = B(s) + 4F- - 1.04  
H2B4O7 + 12H+ + 12e- = 4B(s) + 7H2O - 0.836  
B4O72- + 14H+ + 12e- = 4B(s) + 7H2O - 0.792  

 

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