| Ionization energies for neutral atoms. |
| Z |
|
element |
energy (eV) |
| 1 |
H |
Hydrogen |
13.5984 |
| 2 |
He |
Helium |
24.5874 |
| 3 |
Li |
Lithium |
5.3917 |
| 4 |
Be |
Beryllium |
9.3227 |
| 5 |
B |
Boron |
8.2980 |
| 6 |
C |
Carbon |
11.2603 |
| 7 |
N |
Nitrogen |
14.5341 |
| 8 |
O |
Oxygen |
13.6181 |
| 9 |
F |
Fluorine |
17.4228 |
| 10 |
Ne |
Neon |
21.5646 |
| 11 |
Na |
Sodium |
5.1391 |
| 12 |
Mg |
Magnesium |
7.6462 |
| 13 |
Al |
Aluminum |
5.9858 |
| 14 |
Si |
Silicon |
8.1517 |
| 15 |
P |
Phosphorus |
10.4867 |
| 16 |
S |
Sulfur |
10.3600 |
| 17 |
Cl |
Chlorine |
12.9676 |
| 18 |
Ar |
Argon |
15.7596 |
| 19 |
K |
Potassium |
4.3407 |
| 20 |
Ca |
Calcium |
6.1132 |
| 21 |
Sc |
Scandium |
6.5615 |
| 22 |
Ti |
Titanium |
6.8281 |
| 23 |
V |
Vanadium |
6.7462 |
| 24 |
Cr |
Chromium |
6.7665 |
| 25 |
Mn |
Manganese |
7.4340 |
| 26 |
Fe |
Iron |
7.9024 |
| 27 |
Co |
Cobalt |
7.8810 |
| 28 |
Ni |
Nickel |
7.6398 |
| 29 |
Cu |
Copper |
7.7264 |
| 30 |
Zn |
Zinc |
9.3942 |
| 31 |
Ga |
Gallium |
5.9993 |
| 32 |
Ge |
Germanium |
7.8994 |
| 33 |
As |
Arsenic |
9.7886 |
| 34 |
Se |
Selenium |
9.7524 |
| 35 |
Br |
Bromine |
11.8138 |
| 36 |
Kr |
Krypton |
13.9996 |
| 37 |
Rb |
Rubidium |
4.1771 |
| 38 |
Sr |
Strontium |
5.6949 |
| 39 |
Y |
Yttrium |
6.2171 |
| 40 |
Zr |
Zirconium |
6.6339 |
| 41 |
Nb |
Niobium |
6.7589 |
| 42 |
Mo |
Molybdenum |
7.0924 |
| 43 |
Tc |
Technetium |
7.28 |
| 44 |
Ru |
Ruthenium |
7.3605 |
| 45 |
Rh |
Rhodium |
7.4589 |
| 46 |
Pd |
Palladium |
8.3369 |
| 47 |
Ag |
Silver |
7.5762 |
| 48 |
Cd |
Cadmium |
8.9938 |
| 49 |
In |
Indium |
5.7864 |
| 50 |
Sn |
Tin |
7.3439 |
| 51 |
Sb |
Antimony |
8.6084 |
| 52 |
Te |
Tellurium |
9.0096 |
| 53 |
I |
Iodine |
10.4513 |
| 54 |
Xe |
Xenon |
12.1298 |
| 55 |
Cs |
Cesium |
3.8939 |
| 56 |
Ba |
Barium |
5.2117 |
| 57 |
La |
Lanthanum |
5.5769 |
| 58 |
Ce |
Cerium |
5.5387 |
| 59 |
Pr |
Praseodymium |
5.473 |
| 60 |
Nd |
Neodymium |
5.5250 |
| 61 |
Pm |
Promethium |
5.582 |
| 62 |
Sm |
Samarium |
5.6436 |
| 63 |
Eu |
Europium |
5.6704 |
| 64 |
Gd |
Gadolinium |
6.1501 |
| 65 |
Tb |
Terbium |
5.8638 |
| 66 |
Dy |
Dysprosium |
5.9389 |
| 67 |
Ho |
Holmium |
6.0215 |
| 68 |
Er |
Erbium |
6.1077 |
| 69 |
Tm |
Thulium |
6.1843 |
| 70 |
Yb |
Ytterbium |
6.2542 |
| 71 |
Lu |
Lutetium |
5.4259 |
| 72 |
Hf |
Hafnium |
6.8251 |
| 73 |
Ta |
Tantalum |
7.5496 |
| 74 |
W |
Tungsten |
7.8640 |
| 75 |
Re |
Rhenium |
7.8335 |
| 76 |
Os |
Osmium |
8.4382 |
| 77 |
Ir |
Iridium |
8.9670 |
| 78 |
Pt |
Platinum |
8.9587 |
| 79 |
Au |
Gold |
9.2255 |
| 80 |
Hg |
Mercury |
10.4375 |
| 81 |
Tl |
Thallium |
6.1082 |
| 82 |
Pb |
Lead |
7.4167 |
| 83 |
Bi |
Bismuth |
7.2856 |
| 84 |
Po |
Polonium |
8.417 |
| 85 |
At |
Astatine |
? |
| 86 |
Rn |
Radon |
10.7485 |
| 87 |
Fr |
Francium |
4.0727 |
| 88 |
Ra |
Radium |
5.2784 |
| 89 |
Ac |
Actinium |
5.17 |
| 90 |
Th |
Thorium |
6.3067 |
| 91 |
Pa |
Protactinium |
5.89 |
| 92 |
U |
Uranium |
6.1941 |
| 93 |
Np |
Neptunium |
6.2657 |
| 94 |
Pu |
Plutonium |
6.0262 |
| 95 |
Am |
Americium |
5.9738 |
| 96 |
Cm |
Curium |
5.9915 |
| 97 |
Bk |
Berkelium |
6.1979 |
| 98 |
Cf |
Californium |
6.2817 |
| 99 |
Es |
Einsteinium |
6.42 |
| 100 |
Fm |
Fermium |
6.50 |
| 101 |
Md |
Mendelevium |
6.58 |
| 102 |
No |
Nobelium |
6.65 |
| 103 |
Lr |
Lawrencium |
4.9 |
| 104 |
Rf |
Rutherfordium |
6.0 |
| Source: NIST Ground Levels and Ionization Energies |