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Atomic Reference Data
for Electronic Structure Calculations

Electronic configurations of the elements

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.

    Electronic Configuration
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

Sources:

  1. 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).
  2. C.E. Moore, Ionization Potentials and Ionization Limits Derived from the Analyses of Optical Spectra, Natl. Stand. Ref. Data Ser., Natl. Bur. Stand.(U.S.), 34 (1970).
  3. J. Wyart, Opt. Pura Apl. (Spain) 10, 177 (1977); C. Kiess, J. Res. Nat. Bur. Standards 66A, 111 (1962).
  4. D.D. Lann, J. Res. Nat. Bur. Standards 68A, 207 (1964).
  5. W.F. Meggers, J. Res. Nat. Bur. Standards 61, 441 (1958).
  6. Th. A.M. van Kleef and P.F.A. Klinkenberg, Physica 27, 83 (1961).
  7. Th. A.M. van Kleef and B.C. Matsh, Physica 95C, 251 (1978).
  8. G.W. Charles, J. Opt. Soc. Am. 56, 1292 (1966).
  9. Estimate of present authors.
  10. C. Moore Atomic Energy Levels, NBS 35 3 (1971).
  11. Estimate of present authors.
  12. J. Blaise and J.-F. Wyart Energy levels and atomic spectra of actinides, International Tables of Selected Constants 20, Tables de Constantes (Paris, France 1992).

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