The ground electronic configurations of the neutral elements used here are obtained from the most recent compilation [1] produced by the NIST Atomic Physics Division. Some of these differ from those found in older references. The ground electronic configurations of first cations are in most cases obtained from a previous compilation [2]. There are several cases for which that work gives no identification of configuration, and for these we have used identifications made in the scientific literature. The cases concerned are: Ta+ [3], W+ [4], Re+ [5], Os+ [6], Ir+ [7], Po+ [8], At+ [9], Rn+ [10], Fr+ [11], Pa+ [12], and U+ [12].
The ground electronic configurations of the elements H through U and their first cations are given below. The notation [X] indicates that all subshells associated with the noble gas X are fully occupied.
| Z | Symbol | Neutral | Positive ion |
|---|---|---|---|
| 1 | H | 1s1 | - |
| 2 | He | 1s2 | 1s1 |
| 3 | Li | [He] 2s1 | 1s2 |
| 4 | Be | [He] 2s2 | [He] 2s1 |
| 5 | B | [He] 2s2 2p1 | [He] 2s2 |
| 6 | C | [He] 2s2 2p2 | [He] 2s2 2p1 |
| 7 | N | [He] 2s2 2p3 | [He] 2s2 2p2 |
| 8 | O | [He] 2s2 2p4 | [He] 2s2 2p3 |
| 9 | F | [He] 2s2 2p5 | [He] 2s2 2p4 |
| 10 | Ne | [He] 2s2 2p6 | [He] 2s2 2p5 |
| 11 | Na | [Ne] 3s1 | [He] 2s2 2p6 |
| 12 | Mg | [Ne] 3s2 | [Ne] 3s1 |
| 13 | Al | [Ne] 3s2 3p1 | [Ne] 3s2 |
| 14 | Si | [Ne] 3s2 3p2 | [Ne] 3s2 3p1 |
| 15 | P | [Ne] 3s2 3p3 | [Ne] 3s2 3p2 |
| 16 | S | [Ne]3s2 3p4 | [Ne] 3s2 3p3 |
| 17 | Cl | [Ne] 3s2 3p5 | [Ne] 3s2 3p4 |
| 18 | Ar | [Ne] 3s2 3p6 | [Ne] 3s2 3p5 |
| 19 | K | [Ar] 4s1 | [Ne] 3s2 3p6 |
| 20 | Ca | [Ar] 4s2 | [Ar] 4s1 |
| 21 | Sc | [Ar] 3d1 4s2 | [Ar] 3d1 4s1 |
| 22 | Ti | [Ar] 3d2 4s2 | [Ar] 3d2 4s1 |
| 23 | V | [Ar] 3d3 4s2 | [Ar] 3d4 |
| 24 | Cr | [Ar] 3d5 4s1 | [Ar] 3d5 |
| 25 | Mn | [Ar] 3d5 4s2 | [Ar] 3d5 4s1 |
| 26 | Fe | [Ar] 3d6 4s2 | [Ar] 3d6 4s1 |
| 27 | Co | [Ar] 3d7 4s2 | [Ar] 3d8 |
| 28 | Ni | [Ar] 3d8 4s2 | [Ar] 3d9 |
| 29 | Cu | [Ar] 3d10 4s1 | [Ar] 3d10 |
| 30 | Zn | [Ar] 3d10 4s2 | [Ar] 3d10 4s1 |
| 31 | Ga | [Ar] 3d10 4s2 4p1 | [Ar] 3d10 4s2 |
| 32 | Ge | [Ar] 3d10 4s2 4p2 | [Ar] 3d10 4s2 4p1 |
| 33 | As | [Ar] 3d10 4s2 4p3 | [Ar] 3d10 4s2 4p2 |
| 34 | Se | [Ar] 3d10 4s2 4p4 | [Ar] 3d10 4s2 4p3 |
| 35 | Br | [Ar] 3d10 4s2 4p5 | [Ar] 3d10 4s2 4p4 |
| 36 | Kr | [Ar] 3d10 4s2 4p6 | [Ar] 3d10 4s2 4p5 |
| 37 | Rb | [Kr] 5s1 | [Ar] 3d10 4s2 4p6 |
| 38 | Sr | [Kr] 5s2 | [Kr] 5s1 |
| 39 | Y | [Kr] 4d1 5s2 | [Kr] 5s2 |
| 40 | Zr | [Kr] 4d2 5s2 | [Kr] 4d2 5s1 |
| 41 | Nb | [Kr] 4d4 5s1 | [Kr] 4d4 |
| 42 | Mo | [Kr] 4d5 5s1 | [Kr] 4d5 |
| 43 | Tc | [Kr] 4d5 5s2 | [Kr] 4d5 5s1 |
| 44 | Ru | [Kr] 4d7 5s1 | [Kr] 4d7 |
| 45 | Rh | [Kr] 4d8 5s1 | [Kr] 4d8 |
| 46 | Pd | [Kr] 4d10 | [Kr] 4d9 |
| 47 | Ag | [Kr] 4d10 5s1 | [Kr] 4d10 |
| 48 | Cd | [Kr] 4d10 5s2 | [Kr] 4d10 5s1 |
| 49 | In | [Kr] 4d10 5s2 5p1 | [Kr] 4d10 5s2 |
| 50 | Sn | [Kr] 4d10 5s2 5p2 | [Kr] 4d10 5s2 5p1 |
| 51 | Sb | [Kr] 4d10 5s2 5p3 | [Kr] 4d10 5s2 5p2 |
| 52 | Te | [Kr] 4d10 5s2 5p4 | [Kr] 4d10 5s2 5p3 |
| 53 | I | [Kr] 4d10 5s2 5p5 | [Kr] 4d10 5s2 5p4 |
| 54 | Xe | [Kr] 4d10 5s2 5p6 | [Kr] 4d10 5s2 5p5 |
| 55 | Cs | [Xe] 6s1 | [Kr] 4d10 5s2 5p6 |
| 56 | Ba | [Xe] 6s2 | [Xe] 6s1 |
| 57 | La | [Xe] 5d1 6s2 | [Xe] 5d2 |
| 58 | Ce | [Xe] 4f1 5d1 6s2 | [Xe] 4f1 5d2 |
| 59 | Pr | [Xe] 4f3 6s2 | [Xe] 4f3 6s1 |
| 60 | Nd | [Xe] 4f4 6s2 | [Xe] 4f4 6s1 |
| 61 | Pm | [Xe] 4f5 6s2 | [Xe] 4f5 6s1 |
| 62 | Sm | [Xe] 4f6 6s2 | [Xe] 4f6 6s1 |
| 63 | Eu | [Xe] 4f7 6s2 | [Xe] 4f7 6s1 |
| 64 | Gd | [Xe] 4f7 5d1 6s2 | [Xe] 4f7 5d1 6s1 |
| 65 | Tb | [Xe] 4f9 6s2 | [Xe] 4f9 6s1 |
| 66 | Dy | [Xe] 4f10 6s2 | [Xe] 4f10 6s1 |
| 67 | Ho | [Xe] 4f11 6s2 | [Xe] 4f11 6s1 |
| 68 | Er | [Xe] 4f12 6s2 | [Xe] 4f12 6s1 |
| 69 | Tm | [Xe] 4f13 6s2 | [Xe] 4f13 6s1 |
| 70 | Yb | [Xe] 4f14 6s2 | [Xe] 4f14 6s1 |
| 71 | Lu | [Xe] 4f14 5d1 6s2 | [Xe] 4f14 6s2 |
| 72 | Hf | [Xe] 4f14 5d2 6s2 | [Xe] 4f14 5d1 6s2 |
| 73 | Ta | [Xe] 4f14 5d3 6s2 | [Xe] 4f14 5d3 6s1 |
| 74 | W | [Xe] 4f14 5d4 6s2 | [Xe] 4f14 5d4 6s1 |
| 75 | Re | [Xe] 4f14 5d5 6s2 | [Xe] 4f14 5d5 6s1 |
| 76 | Os | [Xe] 4f14 5d6 6s2 | [Xe] 4f14 5d6 6s1 |
| 77 | Ir | [Xe] 4f14 5d7 6s2 | [Xe] 4f14 5d7 6s1 |
| 78 | Pt | [Xe] 4f14 5d9 6s1 | [Xe] 4f14 5d9 |
| 79 | Au | [Xe] 4f14 5d10 6s1 | [Xe] 4f14 5d10 |
| 80 | Hg | [Xe] 4f14 5d10 6s2 | [Xe] 4f14 5d10 6s1 |
| 81 | Tl | [Xe] 4f14 5d10 6s2 6p1 | [Xe] 4f14 5d10 6s2 |
| 82 | Pb | [Xe] 4f14 5d10 6s2 6p2 | [Xe] 4f14 5d10 6s2 6p1 |
| 83 | Bi | [Xe] 4f14 5d10 6s2 6p3 | [Xe] 4f14 5d10 6s2 6p2 |
| 84 | Po | [Xe] 4f14 5d10 6s2 6p4 | [Xe] 4f14 5d10 6s2 6p3 |
| 85 | At | [Xe] 4f14 5d10 6s2 6p5 | [Xe] 4f14 5d10 6s2 6p4 |
| 86 | Rn | [Xe] 4f14 5d10 6s2 6p6 | [Xe] 4f14 5d10 6s2 6p5 |
| 87 | Fr | [Rn] 7s1 | [Xe] 4f14 5d10 6s2 6p6 |
| 88 | Ra | [Rn] 7s2 | [Rn] 7s1 |
| 89 | Ac | [Rn] 6d1 7s2 | [Rn] 7s2 |
| 90 | Th | [Rn] 6d2 7s2 | [Rn] 6d2 7s1 |
| 91 | Pa | [Rn] 5f2 6d1 7s2 | [Rn] 5f2 7s2 |
| 92 | U | [Rn] 5f3 6d1 7s2 | [Rn] 5f3 7s2 |
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Sources:
- W.C. Martin and W.L. Wiese, "Atomic Spectroscopy," in Atomic, Molecular, and Optical Physics Handbook, ed. G.W.F. Drake, American Institute of Physics (Woodbury NY 1996).
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- Estimate of present authors.
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- Estimate of present authors.
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