• Class: Non-Metals
• Period: 2
• IUPAC group: 13
• Traditional: IIIb

• Discovered in: 1808 by Davy, Gay-Lussac, Thenard
• Origin of name: Arabic: Buraq; Persian: Burah
• Historical or alternate name:

Not free in nature; borax, colemanite, ulexite & rasorite or kernite

Dark powder; unreactive with oxygen, water, alkalis or acids. Combines with most metals to form borides.

• Atmosphere: ~0.0 ppm
• Primitive mantle: 0.6 ppm
• Sea water: 4.8 ppm
• Metallic meteorite: 1.25 ppm
• Continental crust: 10.0 ppm
• Solar photosphere: <2.1 log of abundance
• Oceanic crust: 4.0 ppm
• Solar system: 24.0 relative to Si=1.0e6

   Hazards

Toxic. Compounds may be toxic by ingestion. Halides toxic by inhalation and cause burns..

   Human daily limits

• Lower:1.0
• Upper:100.0

Boron Physical Properties

 Transitional Data

• State: Solid
• Density: 2.34 g/cm3

 Molar enthalpy

• Atomization: 557.64 kJ mol-1
• Fusion: 22.2 kJ mol-1
• Vaporization: 504.5 kJ mol-1

 Transition points

• Melting point: 2573.0 K
• Boiling point: 3931.0 K
• Critical temperature: 3284.0 K

 Molar properties

• Atomic weight: 10.811 g/mole
• Molar volume: 4.718 cm3 mol-1

 Crystal structure sequence

complex-tetragonal <1773 K < complex-rhombohedral < melting point

 Thermodynamics

• State: gas
  • Enthalpy 562.7
  • Gibbs function 518.8
  • Entropy 153.45
  • Heat Capacity 20.799

• State: solid
  • Enthalpy 0
  • Gibbs function 0
  • Entropy 5.86
  • Heat Capacity 11.09

 Miscellaneous physical

• Electrical resistivity: 1.8e12 µ-ohms/cm
• Debye temperature: K
• Thermal conductivity: 27.0 W / m / K
• Coefficient of linear expansion: 4.7Coef. per K
• Mass magnetic susceptibility: -7.8e-9
• X-ray diffraction mass absorption coefficients:
• CuK: 2.39 (µ/p)/cm2 g-1
• MoK: 0.392 (µ/p)/cm2 g-1

Boron Chemical Properties

 Chemical basics:

• Oxidation states: +3
• Molecular wt: 10.811 g/mole

 Radii

• Covalent: 88 pm
• Atomic: 83.0 pm
• Van der Waals: 208 pm

 Ions:

• ion: +3 pm 23.0

 Covalent bonds

 Effective nuclear charge

• Slater: 2.60
• Clementi: 2.42
• Froese-Fischer: 2.27

 Electronegativity

• Pauling: 2.0
• Allred-Rochow: 2.01

 Standard reactions

Boron Nuclear Properties

• Known 6
• Listed 2

• Known 8 - 13
• Listed 10 - 11

• % Occ.:Natural 19.9%
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 3/0
• Radioisotopes:
  • Half-life:
  • Decay mode:
  • Source:
• Notes

• % Occ.:Natural 80.1%
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 3/2
• Radioisotopes:
  • Half-life:
  • Decay mode:
  • Source:
• Notes

• Isotope 10Cross-section 3837 barns
• Isotope 11Cross-section 0.005 barns

• Absolute sensitivity: 3.90e-3 1H=1.0
• Relative sensitivity: 1.99e-2 1H=1.0
• Receptivity: 22.1 13C=1.0
• Magnetogyric ratio: 2.8740e7 rad / T / s
• Quadropole moment: 7.4e-30 m2
• Frequency: 10.746 MHz
• Reference: Et2O/BF3

Boron Energy Properties

Electrons

• Ground state electron configuration: 1s2 2s2 2p1
• Electron affinity: 23 kJ mol-1
• Filling orbitals:

Spectral lines

 Ionization energies

 Atomic energy levels