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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. 5646   Harth et al. (1985)
11  Na Sodium [Ne] 3s 2S1/2 5. 1391   Ciocca et al. (1992)
12  Mg Magnesium [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   Kaufman & Martin (1993)
17  Cl Chlorine [Ne]3s2 3p5 2Po3/2 12. 9676   Radziemski & Kaufman (1969)
18  Ar Argon [Ne]3s2 3p6 1S0 15. 7596   Minnhagen (1973)
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] 3d104s 2S1/2 7. 7264   (1948), (1980), (1999)
30  Zn Zinc [Ar]3d104s2 1S0 9. 3942   Brown et al. (1975)
31  Ga Gallium [Ar]3d104s2 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 4p 5 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. 2171   Garton et al. (1973)
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] 4d105s 2S1/2 7. 5762   (1940), (1999)
48  Cd Cadmium [Kr]4d105s2 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   Knight & Wang (1985)
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. 6436   Worden et al. (1978)
63  Eu Europium [Xe]4f 7     6s2 8So7/2 5. 6704   (1976), (1978)
64  Gd Gadolinium [Xe]4f 7 5d  6s2 9Do2 6. 1501   Worden et al. (1978)
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 145d 2 6s2 3F2 6. 8251   Callender et al. (1988)
73  Ta Tantalum [Xe]4f 145d 3 6s2 4F3/2 7. 5496   Simard et al. (1994)
74  W Tungsten [Xe]4f 145d 4 6s2 5D0 7. 8640   Campbell-Miller & Simard (1996)
75  Re Rhenium [Xe]4f 145d 5 6s2 6S5/2 7. 8335   Campbell-Miller & Simard (1996)
76  Os Osmium [Xe]4f 145d 6 6s2 5D4 8. 4382   Colarusso et al. (1997)
77  Ir Iridium [Xe]4f 145d 7 6s2 4F9/2 8. 9670   Colarusso et al. (1997)
78  Pt Platinum [Xe]4f 145d 9 6s 3D3 8. 9587   Marijnissen et al. (1995)
79  Au Gold [Xe]4f 14 5d10 6s 2S1/2 9. 2255   (1978), (1999)
80  Hg Mercury [Xe]4f 145d10 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. 2856   Young et al. (1980)
84  Po Polonium [Xe]4f 14 5d10 6s2 6p4 3P2 8. 417 ?   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. 0262   (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. 9915   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 146d 2 7s2 ? 3F2 ? 6. 0 ?  Eliav et al. (1995)

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