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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.

ZSymbolNeutralPositive ion
3Li[He] 2s11s2
4Be[He] 2s2[He] 2s1
5B[He] 2s2 2p1[He] 2s2
6C[He] 2s2 2p2[He] 2s2 2p1
7N[He] 2s2 2p3[He] 2s2 2p2
8O[He] 2s2 2p4[He] 2s2 2p3
9F[He] 2s2 2p5[He] 2s2 2p4
10Ne[He] 2s2 2p6[He] 2s2 2p5
11Na[Ne] 3s1[He] 2s2 2p6
12Mg[Ne] 3s2[Ne] 3s1
13Al[Ne] 3s2 3p1[Ne] 3s2
14Si[Ne] 3s2 3p2[Ne] 3s2 3p1
15P[Ne] 3s2 3p3[Ne] 3s2 3p2
16S[Ne]3s2 3p4[Ne] 3s2 3p3
17Cl[Ne] 3s2 3p5[Ne] 3s2 3p4
18Ar[Ne] 3s2 3p6[Ne] 3s2 3p5
19K[Ar] 4s1[Ne] 3s2 3p6
20Ca[Ar] 4s2[Ar] 4s1
21Sc[Ar] 3d1 4s2[Ar] 3d1 4s1
22Ti[Ar] 3d2 4s2[Ar] 3d2 4s1
23V[Ar] 3d3 4s2[Ar] 3d4
24Cr[Ar] 3d5 4s1[Ar] 3d5
25Mn[Ar] 3d5 4s2[Ar] 3d5 4s1
26Fe[Ar] 3d6 4s2[Ar] 3d6 4s1
27Co[Ar] 3d7 4s2[Ar] 3d8
28Ni[Ar] 3d8 4s2[Ar] 3d9
29Cu[Ar] 3d10 4s1[Ar] 3d10
30Zn[Ar] 3d10 4s2[Ar] 3d10 4s1
31Ga[Ar] 3d10 4s2 4p1[Ar] 3d10 4s2
32Ge[Ar] 3d10 4s2 4p2[Ar] 3d10 4s2 4p1
33As[Ar] 3d10 4s2 4p3[Ar] 3d10 4s2 4p2
34Se[Ar] 3d10 4s2 4p4[Ar] 3d10 4s2 4p3
35Br[Ar] 3d10 4s2 4p5[Ar] 3d10 4s2 4p4
36Kr[Ar] 3d10 4s2 4p6[Ar] 3d10 4s2 4p5
37Rb[Kr] 5s1[Ar] 3d10 4s2 4p6
38Sr[Kr] 5s2[Kr] 5s1
39Y[Kr] 4d1 5s2[Kr] 5s2
40Zr[Kr] 4d2 5s2[Kr] 4d2 5s1
41Nb[Kr] 4d4 5s1[Kr] 4d4
42Mo[Kr] 4d5 5s1[Kr] 4d5
43Tc[Kr] 4d5 5s2[Kr] 4d5 5s1
44Ru[Kr] 4d7 5s1[Kr] 4d7
45Rh[Kr] 4d8 5s1[Kr] 4d8
46Pd[Kr] 4d10[Kr] 4d9
47Ag[Kr] 4d10 5s1[Kr] 4d10
48Cd[Kr] 4d10 5s2[Kr] 4d10 5s1
49In[Kr] 4d10 5s2 5p1[Kr] 4d10 5s2
50Sn[Kr] 4d10 5s2 5p2[Kr] 4d10 5s2 5p1
51Sb[Kr] 4d10 5s2 5p3[Kr] 4d10 5s2 5p2
52Te[Kr] 4d10 5s2 5p4[Kr] 4d10 5s2 5p3
53I[Kr] 4d10 5s2 5p5[Kr] 4d10 5s2 5p4
54Xe[Kr] 4d10 5s2 5p6[Kr] 4d10 5s2 5p5
55Cs[Xe] 6s1[Kr] 4d10 5s2 5p6
56Ba[Xe] 6s2[Xe] 6s1
57La[Xe] 5d1 6s2[Xe] 5d2
58Ce[Xe] 4f1 5d1 6s2[Xe] 4f1 5d2
59Pr[Xe] 4f3 6s2[Xe] 4f3 6s1
60Nd[Xe] 4f4 6s2[Xe] 4f4 6s1
61Pm[Xe] 4f5 6s2[Xe] 4f5 6s1
62Sm[Xe] 4f6 6s2[Xe] 4f6 6s1
63Eu[Xe] 4f7 6s2[Xe] 4f7 6s1
64Gd[Xe] 4f7 5d1 6s2[Xe] 4f7 5d1 6s1
65Tb[Xe] 4f9 6s2[Xe] 4f9 6s1
66Dy[Xe] 4f10 6s2[Xe] 4f10 6s1
67Ho[Xe] 4f11 6s2[Xe] 4f11 6s1
68Er[Xe] 4f12 6s2[Xe] 4f12 6s1
69Tm[Xe] 4f13 6s2[Xe] 4f13 6s1
70Yb[Xe] 4f14 6s2[Xe] 4f14 6s1
71Lu[Xe] 4f14 5d1 6s2[Xe] 4f14 6s2
72Hf[Xe] 4f14 5d2 6s2[Xe] 4f14 5d1 6s2
73Ta[Xe] 4f14 5d3 6s2[Xe] 4f14 5d3 6s1
74W[Xe] 4f14 5d4 6s2[Xe] 4f14 5d4 6s1
75Re[Xe] 4f14 5d5 6s2[Xe] 4f14 5d5 6s1
76Os[Xe] 4f14 5d6 6s2[Xe] 4f14 5d6 6s1
77Ir[Xe] 4f14 5d7 6s2[Xe] 4f14 5d7 6s1
78Pt[Xe] 4f14 5d9 6s1[Xe] 4f14 5d9
79Au[Xe] 4f14 5d10 6s1[Xe] 4f14 5d10
80Hg[Xe] 4f14 5d10 6s2[Xe] 4f14 5d10 6s1
81Tl[Xe] 4f14 5d10 6s2 6p1[Xe] 4f14 5d10 6s2
82Pb[Xe] 4f14 5d10 6s2 6p2[Xe] 4f14 5d10 6s2 6p1
83Bi[Xe] 4f14 5d10 6s2 6p3[Xe] 4f14 5d10 6s2 6p2
84Po[Xe] 4f14 5d10 6s2 6p4[Xe] 4f14 5d10 6s2 6p3
85At[Xe] 4f14 5d10 6s2 6p5[Xe] 4f14 5d10 6s2 6p4
86Rn[Xe] 4f14 5d10 6s2 6p6[Xe] 4f14 5d10 6s2 6p5
87Fr[Rn] 7s1[Xe] 4f14 5d10 6s2 6p6
88Ra[Rn] 7s2[Rn] 7s1
89Ac[Rn] 6d1 7s2[Rn] 7s2
90Th[Rn] 6d2 7s2[Rn] 6d2 7s1
91Pa[Rn] 5f2 6d1 7s2[Rn] 5f2 7s2
92U[Rn] 5f3 6d1 7s2[Rn] 5f3 7s2

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  9. Estimate of present authors.
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  11. Estimate of present authors.
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Created October 15, 2015, Updated June 2, 2021