• Class: Transition Metals
• Period: 4
• IUPAC group: 6
• Traditional: VIa

• Discovered in: 1797 by Vauquelin
• Origin of name: Greek: chroma, (color)
• Historical or alternate name:

Chromite ore

Blue-white to silver grey, lustrous metal. Hard and brittle.

• Atmosphere: ~0.0 ppm
• Primitive mantle: 3000.0 ppm
• Sea water: 5e-5 ppm
• Metallic meteorite: 2650.0 ppm
• Continental crust: 185.0 ppm
• Solar photosphere: 5.71 log of abundance
• Oceanic crust: 270.0 ppm
• Solar system: 13400.0 relative to Si=1.0e6

   Hazards

Toxic. Irritant. Carcinogen. Hexavalent compounds toxic by skin contact..

• Lower:0.01
• Upper:1.0

Chromium Physical Properties

 Transitional Data

• State: Solid
• Density: 7.2 g/cm3

 Molar enthalpy

• Atomization: 394.51 kJ mol-1
• Fusion: 15.3 kJ mol-1
• Vaporization: 341.8 kJ mol-1

 Transition points

• Melting point: 2130.0 K
• Boiling point: 2946.0 K
• Critical temperature: 4700.0 K

 Molar properties

• Atomic weight: 51.9961 g/mole
• Molar volume: 7.274 cm3 mol-1

 Crystal structure sequence

body-centered-cubic

 Thermodynamics

• State: solid
  • Enthalpy 0
  • Gibbs function 0
  • Entropy 23.47
  • Heat Capacity 23.35

• State: gas
  • Enthalpy 396.6
  • Gibbs function 351.8
  • Entropy 174.50
  • Heat Capacity 20.79

 Miscellaneous physical

• Electrical resistivity: 12.9 µ-ohms/cm
• Debye temperature: 630.0 K
• Thermal conductivity: 93.7 W / m / K
• Coefficient of linear expansion: 4.5Coef. per K
• Mass magnetic susceptibility: 4.45e-8
• X-ray diffraction mass absorption coefficients:
• CuK: 260 (µ/p)/cm2 g-1
• MoK: 31.1 (µ/p)/cm2 g-1

Chromium Chemical Properties

 Chemical basics:

• Oxidation states: +2 +3 +4 +5 +6
• Molecular wt: 51.9961 g/mole

 Radii

• Covalent: pm
• Atomic: 129.0 pm
• Van der Waals: pm

 Ions:

• ion: +2 pm 80.0
• ion: +3 pm 61.5
• ion: +4 pm 55.0
• ion: +5 pm 49.0
• ion: +6 pm 44.0

 Covalent bonds

 Effective nuclear charge

• Slater: 3.45
• Clementi: 5.13
• Froese-Fischer: 6.92

 Electronegativity

• Pauling: 1.6
• Allred-Rochow: 1.56

 Standard reactions

Chromium Nuclear Properties

• Known 9
• Listed 5

• Known 48 - 56
• Listed 50 - 54

• % Occ.:Natural 4.345%
• Mossbauer NRA:
• Nuclear spin/Quantum no.:
• Radioisotopes:
  • Half-life:
  • Decay mode:
  • Source:
• Notes

• % Occ.:Natural
• Mossbauer NRA:
• Nuclear spin/Quantum no.:
• Radioisotopes:
  • Half-life: 27.7 days
  • Decay mode: E.C.,
  • Source:
• Notes med

• % Occ.:Natural 83.789%
• Mossbauer NRA:
• Nuclear spin/Quantum no.:
• Radioisotopes:
  • Half-life:
  • Decay mode:
  • Source:
• Notes

• % Occ.:Natural 9.501%
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 3/2
• Radioisotopes:
  • Half-life:
  • Decay mode:
  • Source:
• Notes

• % Occ.:Natural 2.365%
• Mossbauer NRA:
• Nuclear spin/Quantum no.:
• Radioisotopes:
  • Half-life:
  • Decay mode:
  • Source:
• Notes

• Isotope Cross-section 3.1±0.2 barns

• Absolute sensitivity: 8.62e-3 1H=1.0
• Relative sensitivity: 9.03e-4 1H=1.0
• Receptivity: 0.49 13C=1.0
• Magnetogyric ratio: -1.5120e7 rad / T / s
• Quadropole moment: ±0.3e-28 m2
• Frequency: 5.652 MHz
• Reference: CrO4-2

Chromium Energy Properties

Electrons

• Ground state electron configuration: [Ar] 3d5 4s1
• Electron affinity: 94 kJ mol-1
• Filling orbitals:

Spectral lines

 Ionization energies

 Atomic energy levels