Industrial Mineral Boron

A New Vision of Boron

Boron is an element on the periodic table with symbol B, atomic number 5, and atomic weight 10.81. Located in the 3A group of the periodic table, boron is a semiconductor metalloid. Boron occurs naturally in the form of two stable isotopes, namely B10 and B11. For the B10 isotope, the natural rate of occurrence is 19.1–20.3%, whereas for the B11 it is 79.7–80.9%.

Chemically unbound boron cannot be found naturally on Earth. It forms compounds with various metallic and non-metallic elements of different characteristics. Thus, many boron compounds can be used in different industries. When forming other compounds, boron acts like a non-metallic compound. Pure boron, on the other hand, is an electrical conductor just like carbon. Optically and visually, crystallized boron exhibits structures like diamonds and it is almost equally hard. Pure boron was first isolated by the French chemists, J.L. Gay-Lussac and Baron L.J. Thenard, and the British chemist, H. Davy, in 1808.

ATOMIC STRUCTURE

• Atomic radius: 1.17 Å
• Atomic volume: 4.6 cm³/mol
• Crystal structure: Rhombohedral
• Electron configuration: 1s2 2s2 p1
• Ionic radius: 0.23 Å
• Number of electrons (neutral): 5
• Number of neutrons: 6
• Number of protons: 5
• Valence electrons: 2s2 p1

CHEMICAL PROPERTIES

• Electrochemical equivalence: 0.1344 g/amp-hr
• Electronegativity (Pauling): 2.04
• Heat of fusion: 50.2 kJ/mol
• Ionization potential:
  • First: 8.298
  • Second: 25.154
  • Third: 37.93
• Valence electron potential (-eV): 190

PHYSICAL PROPERTIES

• Atomic mass: 10.811
• Boiling point: 4.275 K – 4.002 °C – 7.236 °F
• Thermal expansion coefficient: 0.0000083 cm/cm/°C (0 °C)
• Conductivity:
  • Electrical: 1.0 E –12,106/cm
  • Thermal: 0.274 W/cmK
• Density: 2.34 g/cc @ 300 K
• Appearance: Yellow-brown non-metallic crystal
• Elastic modulus:
  • Bulk: 320/GPa
• Enthalpy of atomization: 573.2 kJ/mol @ 25 °C
• Enthalpy of fusion: 22.18 kJ/mol
• Enthalpy of vaporization: 480 kJ/mol
• Hardness:
  • Mohs: 9.3
  • Vickers: 49,000 MN m-2
• Heat of vaporization: 489.7 kJ/mol
• Fusion temperature: 2,573 K – 2,300 °C – 4,172 °F
• Molar mass: 4.68 cm³/mol
• Phase at STP (20 °C & 1 atm): Solid
• Specific heat: 1.02 J/gK
• Vapor pressure: 0.348 Pa @ 2,300 °C