Ionisation Energies

The first ionisation energy is the energy which is necessary to remove one electron from an atom in the ground state. In general metals have a low ionisation energy and non-metals have a high ionisation energy. The noble gases Helium and Neon have the highest ionisation energies. Caesium and Francium have the lowest ionisation energies.

The ionisation energies in the table below are given in units of electron volts (eV).

Z	Name	Ionisation Energy [eV]
1	Hydrogen	13.598
2	Helium	24.587
3	Lithium	5.392
4	Beryllium	9.322
5	Boron	8.298
6	Carbon	11.260
7	Nitrogen	14.534
8	Oxygen	13.618
9	Fluorine	17.422
10	Neon	21.564
11	Sodium	5.139
12	Magnesium	7.646
13	Aluminium	5.986
14	Silicon	8.151
15	Phosphorus	10.486
16	Sulfur	10.360
17	Chlorine	12.967
18	Argon	15.759
19	Potassium	4.341
20	Calcium	6.113
21	Scandium	6.54
22	Titanium	6.82
23	Vanadium	6.74
24	Chromium	6.766
25	Manganese	7.435
26	Iron	7.870
27	Cobalt	7.86
28	Nickel	7.635
29	Copper	7.726
30	Zinc	9.394
31	Gallium	5.999
32	Germanium	7.899
33	Arsenic	9.81
34	Selenium	9.752
35	Bromine	11.814
36	Krypton	13.999
37	Rubidium	4.177
38	Strontium	5.695
39	Yttrium	6.38
40	Zirconium	6.84
41	Niobium	6.88
42	Molybdenum	7.099
43	Technetium	7.28
44	Ruthenium	7.37
45	Rhodium	7.46
46	Palladium	8.34
47	Silver	7.576
48	Cadmium	8.993
49	Indium	5.786
50	Tin	7.344
51	Antimony	8.641
52	Tellurium	9.009
53	Iodine	10.451
54	Xenon	12.130
55	Caesium	3.894
56	Barium	5.212
57	Lanthanum	5.577
58	Cerium	5.47
59	Praseodymium	5.42
60	Neodymium	5.49
61	Promethium	5.55
62	Samarium	5.63
63	Europium	5.67
64	Gadolinium	6.14
65	Terbium	5.85
66	Dysprosium	5.93
67	Holmium	6.02
68	Erbium	6.10
69	Thulium	6.18
70	Ytterbium	6.254
71	Lutetium	5.426
72	Hafnium	7.0
73	Tantalum	7.89
74	Tungsten	7.98
75	Rhenium	7.88
76	Osmium	8.7
77	Iridium	9.1
78	Platinum	9.0
79	Gold	9.225
80	Mercury	10.437
81	Thallium	6.108
82	Lead	7.416
83	Bismuth	7.289
84	Polonium	8.42
85	Astatine	9.5
86	Radon	10.748
87	Francium	4.0
88	Radium	5.279
89	Actinium	6.9
90	Thorium	6.95
91	Protactinium	n.n.
92	Uranium	6.08
93	Neptunium	n.n.
94	Plutonium	5.8
95	Americium	6.0
96	Curium	n.n.
97	Berkelium	n.n.
98	Californium	n.n.
99	Einsteinium	n.n.
100	Fermium	n.n.
101	Mendelevium	n.n.
102	Nobelium	n.n.
103	Lawrencium	n.n.
104	Rutherfordium	n.n.
105	Dubnium	n.n.
106	Seaborgium	n.n.
107	Bohrium	n.n.
108	Hassium	n.n.
109	Meitnerium	n.n.
110	Unnunnilium	n.n.
111	Unnununium	n.n.