• Class: Transition Metals
• Period: 5
• IUPAC group: 5
• Traditional: Va

• Discovered in: 1801 by Hatchett
• Origin of name: Niobe (previously Columbium)
• Historical or alternate name:

Niobite or columbite, niobite-tantalite, pyrochlore & euxenite

Silvery, shiny soft metal. Exposed surfaces form oxide film.

• Atmosphere: ~0.0 ppm
• Primitive mantle: 0.56 ppm
• Sea water: 1e-5 ppm
• Metallic meteorite: 0.250 ppm
• Continental crust: 11.0 ppm
• Solar photosphere: 1.9 log of abundance
• Oceanic crust: 2.2 ppm
• Solar system: 0.71 relative to Si=1.0e6

   Hazards

Compounds may be irritants by skin contact..

• Lower:0.01
• Upper:1.0

Niobium Physical Properties

 Transitional Data

• State: Solid
• Density: 8.57 g/cm3

 Molar enthalpy

• Atomization: 722.819 kJ mol-1
• Fusion: 27.2 kJ mol-1
• Vaporization: 680.19 kJ mol-1

 Transition points

• Melting point: 2741.0 K
• Boiling point: 5015.0 K
• Critical temperature: 8700.0 K

 Molar properties

• Atomic weight: 92.90638 g/mole
• Molar volume: 10.895 cm3 mol-1

 Crystal structure sequence

body-centered-cubic

 Thermodynamics

• State: solid
  • Enthalpy 0
  • Gibbs function 0
  • Entropy 36.40
  • Heat Capacity 24.60

• State: gas
  • Enthalpy 725.9
  • Gibbs function 681.1
  • Entropy 186.256
  • Heat Capacity 30.158

 Miscellaneous physical

• Electrical resistivity: 12.5 µ-ohms/cm
• Debye temperature: 275.0 K
• Thermal conductivity: 53.7 W / m / K
• Coefficient of linear expansion: 7.3Coef. per K
• Mass magnetic susceptibility: 2.76e-8
• X-ray diffraction mass absorption coefficients:
• CuK: 153 (µ/p)/cm2 g-1
• MoK: 17.1 (µ/p)/cm2 g-1

Niobium Chemical Properties

 Chemical basics:

• Oxidation states: +3 +4 +5
• Molecular wt: 92.90638 g/mole

 Radii

• Covalent: 134 pm
• Atomic: 147.0 pm
• Van der Waals: pm

 Ions:

• ion: +3 pm 72.0
• ion: +4 pm 68.0
• ion: +5 pm 64.0

 Covalent bonds

 Effective nuclear charge

• Slater: 3.30
• Clementi: 6.70
• Froese-Fischer: 9.60

 Electronegativity

• Pauling: 1.6
• Allred-Rochow: 1.23

 Standard reactions

Niobium Nuclear Properties

• Known 24
• Listed 5

• Known 88 - 101
• Listed 91 - 95

• % Occ.:Natural
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 9/2
• Radioisotopes:
  • Half-life: 680.0 years
  • Decay mode: E.C.,
  • Source: reactor
• Notes

• % Occ.:Natural
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 7/0
• Radioisotopes:
  • Half-life: 36.0 E6 years
  • Decay mode: E.C.,
  • Source: reactor
• Notes

• % Occ.:Natural 100.0%
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 9/2
• Radioisotopes:
  • Half-life:
  • Decay mode:
  • Source:
• Notes

• % Occ.:Natural
• Mossbauer NRA:
• Nuclear spin/Quantum no.: 6/0
• Radioisotopes:
  • Half-life: 200.0 centuries
  • Decay mode: Beta-
  • Source: reactor
• Notes

• % Occ.:Natural
• Mossbauer NRA:
• Nuclear spin/Quantum no.:
• Radioisotopes:
  • Half-life: 35.0 days
  • Decay mode: Beta-
  • Source: reactor
• Notes

• Isotope Cross-section 1.15±0.05 barns

• Absolute sensitivity: 0.48 1H=1.0
• Relative sensitivity: 0.48 1H=1.0
• Receptivity: 2740 13C=1.0
• Magnetogyric ratio: 6.5476e7 rad / T / s
• Quadropole moment: -0.2e-28 m2
• Frequency: 24.442 MHz
• Reference: NbF6-(conc.HF)

Niobium Energy Properties

Electrons

• Ground state electron configuration: [Kr] 4d4 5s1
• Electron affinity: 109 kJ mol-1
• Filling orbitals:

Spectral lines

 Ionization energies

 Atomic energy levels