Thorium: properties of free atoms

Thorium atoms have 90 electrons and the shell structure is

The ground state electron configuration of ground state gaseous neutral thorium is  [Rn].6d2.7s2 and the term symbol is  3F2.

Atomic spectrum


A representation of the atomic spectrum of thorium.

Electronic configuration of neutral atomic thorium

Electronic configuration of thorium

The electronic configuration of thorium.

Kossel shell structure of thorium

The Kossel shell structure of thorium.

Ionisation Energies and electron affinity

The electron affinity of thorium is (no data) kJ mol‑1. The ionisation energies of thorium are given below.

Ionisation energies of thorium
Ionisation energy number Enthalpy / kJ mol‑1

Effective Nuclear Charges

The following are "Clementi-Raimondi" effective nuclear charges, Zeff. Follow the hyperlinks for more details and for graphs in various formats.

Effective nuclear charges for thorium
1s(no data)  
2s(no data) 2p(no data)  
3s(no data) 3p(no data) 3d(no data)  
4s(no data) 4p(no data) 4d(no data) 4f(no data)
5s(no data) 5p(no data) 5d(no data)  
6s(no data) 6p(no data)  


These effective nuclear charges, Zeff, are adapted from the following references:

  1. E. Clementi and D.L.Raimondi, J. Chem. Phys. 1963, 38, 2686.
  2. E. Clementi, D.L.Raimondi, and W.P. Reinhardt, J. Chem. Phys. 1967, 47, 1300.

Electron binding energies

Electron binding energies for thorium. All values of electron binding energies are given in eV. The binding energies are quoted relative to the vacuum level for rare gases and H2, N2, O2, F2, and Cl2 molecules; relative to the Fermi level for metals; and relative to the top of the valence band for semiconductors.
Label Orbital eV [literature reference]
K 1s109651 [1]
L I2s20472 [1]
L II2p1/219693 [1]
L III2p3/216300 [1]
M I3s5182 [1]
M II3p1/24830 [1]
M III3p3/24046 [1]
M IV3d3/23491 [1]
M V3d5/23332 [1]
N I4s1330 [2]
N II4p1/21168 [2]
N III4p3/2966.4 [3]
N IV4d3/2712.1 [3]
N V4d5/2675.2 [3]
N VI4f5/2342.4 [3]
N VII4f7/2333.1 [3]
O I5s290 [2, one-particle approximation not valid owing to short core-hole lifetime]
O II5p1/2229 [2, one-particle approximation not valid owing to short core-hole lifetime]
O III5p3/2182 [2, one-particle approximation not valid owing to short core-hole lifetime]
O IV5d3/292.5 [3]
O V5d5/285.4 [3]
P I6s41.4 [3]
P II6p1/224.5 [3]
P III6p3/216.6 [3]


I am grateful to Gwyn Williams (Jefferson Laboratory, Virginia, USA) who provided the electron binding energy data. The data are adapted from references 1-3. They are tabulated elsewhere on the WWW (reference 4) and in paper form (reference 5).


  1. J. A. Bearden and A. F. Burr, "Reevaluation of X-Ray Atomic Energy Levels," Rev. Mod. Phys., 1967, 39, 125.
  2. M. Cardona and L. Ley, Eds., Photoemission in Solids I: General Principles (Springer-Verlag, Berlin) with additional corrections, 1978.
  3. Gwyn Williams WWW table of values
  4. D.R. Lide, (Ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 81st edition, 2000.
  5. J. C. Fuggle and N. Mårtensson, "Core-Level Binding Energies in Metals," J. Electron Spectrosc. Relat. Phenom., 1980, 21, 275.

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