NIST Physics Laboratory Table of Ground Levels and Ionization Energies for the Neutral Atoms

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Ground levels and ionization energies for the neutral atoms

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Z         Element    Ground-state
configuration
   Ground
   level
Ionization
energy (eV)
   Reference for
ionization energy

1 H Hydrogen 1s         2S1/2 13.5984     (1983), (1985)
2 He Helium 1s2         1S0 24.5874 (1997), (1998)

3 Li Lithium 1s2 2s       2S1/2 5.3917 Lorenzen & Niemax (1982)
4 Be Beryllium 1s2 2s2       1S0 9.3227 Beigang et al. (1983)
5 B Boron 1s2 2s2 2p     2Po1/2 8.2980 (1970), (1974)
6 C Carbon 1s2 2s2 2p2     3P0 11.2603 Johansson (1966)
7 N Nitrogen 1s2 2s2 2p3     4So3/2 14.5341 Eriksson & Pettersson (1971)
8 O Oxygen 1s2 2s2 2p4     3P2 13.6181 Eriksson & Isberg (1968)
9 F Fluorine 1s2 2s2 2p5     2Po3/2 17.4228 (1949), (1969)
10 Ne Neon 1s2 2s2 2p6     1S0 21.5645 Kaufman & Minnhagen (1972)

11 Na Sodium [Ne]  3s       2S1/2 5.1391 (1992), (1998)
12 MgMagnesium [Ne] 3s2       1S0 7.6462 (1987), (1991)
13 Al Aluminum [Ne] 3s2 3p     2Po1/2 5.9858 (1990), (1991)
14 Si Silicon [Ne] 3s2 3p2     3P0 8.1517 Martin & Zalubas (1983)
15 P Phosphorus [Ne] 3s2 3p3     4So3/2 10.4867 Svendenius (1980)
16 S Sulfur [Ne] 3s2 3p4     3P2 10.3600 Martin et al. (1990)
17 Cl Chlorine [Ne] 3s2 3p5     2Po3/2 12.9676 Radziemski & Kaufman (1969)
18 Ar Argon [Ne] 3s2 3p6     1S0 15.7596 Velchev et al. (1999)

19 K Potassium [Ar]   4s     2S1/2 4.3407 (1983), (1985)
20 Ca Calcium [Ar]   4s2     1S0 6.1132 Sugar & Corliss (1985)
21 Sc Scandium [Ar] 3d 4s2     2D3/2 6.5615 Sugar & Corliss (1985)
22 Ti Titanium [Ar] 3d 2 4s2     3F2 6.8281 Sohl et al. (1990)
23 V Vanadium [Ar] 3d 3 4s2     4F3/2 6.7462 James et al. (1994)
24 Cr Chromium [Ar] 3d 5 4s     7S3 6.7665 Sugar & Corliss (1985)
25 Mn Manganese [Ar] 3d 5 4s2     6S5/2 7.4340 Sugar & Corliss (1985)
26 Fe Iron [Ar] 3d 6 4s2     5D4 7.9024 Sugar & Corliss (1985)
27 Co Cobalt [Ar] 3d 7 4s2     4F9/2 7.8810 Page & Gudeman (1990)
28 Ni Nickel [Ar] 3d 8 4s2     3F4 7.6398 Page & Gudeman (1990)
29 Cu Copper [Ar] 3d10 4s     2S1/2 7.7264 (1948), (1980), (1999)
30 Zn Zinc [Ar] 3d10 4s2     1S0 9.3942 Brown et al. (1975)
31 Ga Gallium [Ar] 3d10 4s2 4p   2Po1/2 5.9993 Tursunov & Eshkobilov (1985)
32 Ge Germanium [Ar] 3d10 4s2 4p2   3P0 7.8994 Sugar & Musgrove (1993)
33 As Arsenic [Ar] 3d10 4s2 4p3   4So3/2 9.7886 Bhatia & Jones (1971)
34 Se Selenium [Ar] 3d10 4s2 4p4   3P2 9.7524 (1974), (1983)
35 Br Bromine [Ar] 3d10 4s2 4p5   2Po3/2 11.8138 (1961), (1967)
36 Kr Krypton [Ar] 3d10 4s2 4p6   1S0 13.9996 Sugar & Musgrove (1991)

37 Rb Rubidium [Kr]   5s     2S1/2 4.1771 (1961), (1983)
38 Sr Strontium [Kr]   5s2     1S0 5.6949 Rubbmark & Borgstrom (1978)
39 Y Yttrium [Kr] 4d 5s2     2D3/2 6.2173 (1973), (2000)
40 Zr Zirconium [Kr] 4d 2 5s2     3F2 6.6339 Hackett et al. (1986)
41 Nb Niobium [Kr] 4d 4 5s     6D1/2 6.7589 Rayner et al. (1987)
42 Mo Molybdenum [Kr] 4d 5 5s     7S3 7.0924 Rayner et al. (1987)
43 Tc Technetium [Kr] 4d 5 5s2     6S5/2 7.28     Finkelnburg & Humbach (1955)
44 Ru Ruthenium [Kr] 4d 7 5s     5F5 7.3605 (1979), (1988)
45 Rh Rhodium [Kr] 4d 8 5s     4F9/2 7.4589 Callender et al. (1988)
46 Pd Palladium [Kr] 4d10       1S0 8.3369 Callender et al. (1988)
47 Ag Silver [Kr] 4d10 5s     2S1/2 7.5762 (1940), (1999)
48 Cd Cadmium [Kr] 4d10 5s2     1S0 8.9938 Brown et al. (1975)
49 In Indium [Kr] 4d10 5s2 5p   2Po1/2 5.7864 Dönszelmann & Neijzen (1983)
50 Sn Tin [Kr] 4d10 5s2 5p2   3P0 7.3439 Brown et al. (1977)
51 Sb Antimony [Kr] 4d10 5s2 5p3   4So3/2 8.6084 Beigang & Wynne (1986)
52 Te Tellurium [Kr] 4d10 5s2 5p4   3P2 9.0096 Cantú et al. (1986)
53 I Iodine [Kr] 4d10 5s2 5p5   2Po3/2 10.4513 Minnhagen (1962)
54 Xe Xenon [Kr] 4d10 5s2 5p6   1S0 12.1298 (1985), (2001)

55 Cs Cesium [Xe]     6s   2S1/2 3.8939 Weber & Sansonetti (1984)
56 Ba Barium [Xe]     6s2   1S0 5.2117 Post et al. (1985)
57 La Lanthanum [Xe]   5d 6s2   2D3/2 5.5769 Garton & Wilson (1966)
58 Ce Cerium [Xe] 4f  5d 6s2   1Go4 5.5387 Worden et al. (1978)
59 Pr Praseodymium [Xe] 4f 3   6s2   4Io9/2 5.473   Worden et al. (1978)
60 Nd Neodymium [Xe] 4f 4   6s2   5I4 5.5250 Worden et al. (1978)
61 Pm Promethium [Xe] 4f 5   6s2   6Ho5/2 5.582   Worden et al. (1978)
62 Sm Samarium [Xe] 4f 6   6s2   7F0 5.6437 T. Jaysekharan et al. (2000)
63 Eu Europium [Xe] 4f 7   6s2   8So7/2 5.6704 Nakhate et al. (2000)
64 Gd Gadolinium [Xe] 4f 7 5d 6s2   9Do2 6.1498 Miyabe et al. (1998)
65 Tb Terbium [Xe] 4f 9   6s2   6Ho15/2 5.8638 Worden et al. (1978)
66 Dy Dysprosium [Xe] 4f 10   6s2   5I8 5.9389 Worden et al. (1978)
67 Ho Holmium [Xe] 4f 11   6s2   4Io15/2 6.0215 Worden et al. (1978)
68 Er Erbium [Xe] 4f 12   6s2   3H6 6.1077 Worden et al. (1978)
69 Tm Thulium [Xe] 4f 13   6s2   2Fo7/2 6.1843 Camus (1971)
70 Yb Ytterbium [Xe] 4f 14   6s2   1S0 6.2542 Aymar et al. (1980)
71 Lu Lutetium [Xe] 4f 14 5d 6s2   2D3/2 5.4259 (1972), (1989)
72 Hf Hafnium [Xe] 4f 14 5d 2 6s2   3F2 6.8251 Callender et al. (1988)
73 Ta Tantalum [Xe] 4f 14 5d 3 6s2   4F3/2 7.5496 Simard et al. (1994)
74 W Tungsten [Xe] 4f 14 5d 4 6s2   5D0 7.8640 Campbell-Miller & Simard (1996)
75 Re Rhenium [Xe] 4f 14 5d 5 6s2   6S5/2 7.8335 Campbell-Miller & Simard (1996)
76 Os Osmium [Xe] 4f 14 5d 6 6s2   5D4 8.4382 Colarusso et al. (1997)
77 Ir Iridium [Xe] 4f 14 5d 7 6s2   4F9/2 8.9670 Colarusso et al. (1997)
78 Pt Platinum [Xe] 4f 14 5d 9 6s   3D3 8.9588 (1995), (2000)
79 Au Gold [Xe] 4f 14 5d10 6s   2S1/2 9.2255 (1978), (1999)
80 Hg Mercury [Xe] 4f 14 5d10 6s2   1S0 10.4375 Baig (1983)
81 Tl Thallium [Xe] 4f 14 5d10 6s2 6p 2Po1/2 6.1082 Baig & Connerade (1985)
82 Pb Lead [Xe] 4f 14 5d10 6s2 6p2 3P0 7.4167 Brown et al. (1977)
83 Bi Bismuth [Xe] 4f 14 5d10 6s2 6p3 4So3/2 7.2855 Matthews et al. (1989)
84 Po Polonium [Xe] 4f 14 5d10 6s2 6p4 3P2 8.414   Charles (1966)
85 At Astatine [Xe] 4f 14 5d10 6s2 6p5 2Po3/2    
86 Rn Radon [Xe] 4f 14 5d10  6s2 6p6 1S0 10.7485 (1933), (1970)

87 Fr Francium [Rn]     7s   2S1/2 4.0727 Arnold et al. (1990)
88 Ra Radium [Rn]     7s2   1S0 5.2784 Amstrong et al. (1980)
89 Ac Actinium [Rn]   6d 7s2   2D3/2 5.17     (1955), (1974)
90 Th Thorium [Rn]   6d 2 7s2   3F2 6.3067 Köhler et al. (1997)
91 Pa Protactinium [Rn] 5f 2(3H4) 6d 7s2 (4,3/2)11/2 5.89     Sugar (1974)
92 U Uranium [Rn] 5f 3(4Io9/2) 6d 7s2 (9/2,3/2)o6 6.1941 Coste et al. (1982)
93 Np Neptunium [Rn] 5f 4(5I4) 6d 7s2 (4,3/2)11/2 6.2657 (1979), (1994), (1997)
94 Pu Plutonium [Rn] 5f 6   7s2   7F0 6.0260 (1993), (1997)
95 Am Americium [Rn] 5f 7   7s2   8So7/2 5.9738 Köhler et al. (1997)
96 Cm Curium [Rn] 5f 7 6d 7s2   9Do2 5.9914 Köhler et al. (1997)
97 Bk Berkelium [Rn] 5f 9   7s2   6Ho15/2 6.1979 Köhler et al. (1997)
98 Cf Californium [Rn] 5f 10   7s2   5I8 6.2817 Köhler et al. (1997)
99 Es Einsteinium [Rn] 5f 11   7s2   4Io15/2 6.42     Sugar (1974)
100 Fm Fermium [Rn] 5f 12   7s2   3H6 6.50     Sugar (1974)
101 Md Mendelevium [Rn] 5f 13   7s2   2Fo7/2 6.58     Sugar (1974)
102 No Nobelium [Rn] 5f 14   7s2   1S0 6.65     Sugar (1974)
103 Lr Lawrencium [Rn] 5f 14   7s2 7p ? 2Po1/2 ? 4.9 ?    Eliav et al. (1995)
104 Rf Rutherfordium [Rn] 5f 14  6d 2 7s2 ?   3F2 ? 6.0 ?    Eliav et al. (1995)

Table of Ground Levels and Ionization Energies for the Neutral Atoms