Electron affinity (data page)

This page deals with the electron affinity as a property of isolated atoms or molecules. Solid state electron affinities are not listed here.

Elements

Electron affinity can be defined in two equivalent ways. First, as the energy that is released by adding an electron to an isolated gaseous atom. The second definition is that electron affinity is the energy required to remove an electron from a singly charged gaseous negative ion. The latter can be regarded as the ionization energy of the −1 ion or the zeroth ionization energy. Either convention can be used.
Negative electron affinities can be used in those cases where electron capture requires energy, i.e. when capture can occur only if the impinging electron has a kinetic energy large enough to excite a resonance of the atom-plus-electron system. Conversely electron removal from the anion formed in this way releases energy, which is carried out by the freed electron as kinetic energy. Negative ions formed in these cases are always unstable. They may have lifetimes of the order of microseconds to milliseconds, and invariably autodetach after some time.
† A quantum offset of the velocity imaging-based measurements was revealed in 2025, which could make a revision of all electron affinities marked with a dagger ^† necessary. The value of the downward correction to be applied is determined by the intensity of the electric field that was used in the experiment, which was not published with the original measurements, but can be estimated to be of the order of −20 μeV.

Z	Element	Name	Electron affinity	Electron affinity	References
1	¹H	Hydrogen	0.754 195	72.769
1	²H	Deuterium	0.754 67	72.814
2	He	Helium	−0.5	−48	est.
3	Li	Lithium	0.618 049	59.632 6
4	Be	Beryllium	−0.5	−48	est.
5	B	Boron	0.279 723	26.989
6	¹²C	Carbon	1.262 122 6	121.776 3
6	¹³C	Carbon	1.262 113 6	121.775 5
7	N	Nitrogen	−0.07	−6.8
8	¹⁶O	Oxygen	1.461 112 97	140.975 970
8	¹⁷O	Oxygen	1.461 108	140.975 5
8	¹⁸O	Oxygen	1.461 105	140.975 2
9	F	Fluorine	3.401 189 8	328.164 9
10	Ne	Neon	−1.2	−116	est.
11	Na	Sodium	0.547 926	52.867
12	Mg	Magnesium	−0.4	−40	est.
13	Al	Aluminium	0.432 83	41.762
14	Si	Silicon	1.389 521 2	134.068 4
15	P	Phosphorus	0.746 609	72.037
16	³²S	Sulfur	2.077 104 2	200.410 1
16	³⁴S	Sulfur	2.077 104 5	200.410 1
17	Cl	Chlorine	3.612 725	348.575
18	Ar	Argon	−1.0	−96	est.
19	K	Potassium	0.501 459	48.383
20	Ca	Calcium	0.024 55	2.37
21	Sc	Scandium	0.179 380^†	17.307 6
22	Ti	Titanium	0.075 54^†	7.289
23	V	Vanadium	0.527 66^†	50.911
24	Cr	Chromium	0.675 928^†	65.217 2
25	Mn	Manganese	−0.5	−50	est.
26	Fe	Iron	0.153 236^†	14.785
27	Co	Cobalt	0.662 255^†	63.897 9
28	Ni	Nickel	1.157 16	111.65
29	Cu	Copper	1.235 78	119.235
30	Zn	Zinc	−0.6	−58	est.
31	Ga	Gallium	0.301 166^†	29.058 1
32	Ge	Germanium	1.232 676 4	118.935 2
33	⁷⁵As	Arsenic	0.804 486	77.621 1
34	Se	Selenium	2.020 604 7	194.958 7
35	Br	Bromine	3.363 588	324.536 9
36	Kr	Krypton	−1.0	−96	est.
37	Rb	Rubidium	0.485 916	46.884
38	Sr	Strontium	0.052 06	5.023
39	Y	Yttrium	0.311 29^†	30.035
40	Zr	Zirconium	0.433 28^†	41.806
41	Nb	Niobium	0.917 40^†	88.516
42	Mo	Molybdenum	0.747 23^†	72.097
43	Tc	Technetium	0.55	53	est.
44	Ru	Ruthenium	1.046 27^†	100.950
45	Rh	Rhodium	1.142 89	110.27
46	Pd	Palladium	0.562 14	54.24
47	Ag	Silver	1.304 47	125.862
48	Cd	Cadmium	−0.7	−68	est.
49	In	Indium	0.38392	37.043
50	Sn	Tin	1.112 070	107.298 4
51	Sb	Antimony	1.047 401	101.059
52	Te	Tellurium	1.970 875	190.161
53	¹²⁷I	Iodine	3.059 046 5	295.153 1
53	¹²⁸I	Iodine	3.059 052	295.154
54	Xe	Xenon	−0.8	−77	est.
55	Cs	Caesium	0.4715983	45.5023
56	Ba	Barium	0.144 62	13.954
57	La	Lanthanum	0.557 546^†	53.795
58	Ce	Cerium	0.600 160^†	57.906 7
59	Pr	Praseodymium	0.109 23^†	10.539
60	Nd	Neodymium	0.097 49^†	9.406
61	Pm	Promethium	0.129	12.45
62	Sm	Samarium	0.162	15.63
63	Eu	Europium	0.116	11.2
64	Gd	Gadolinium	0.212^†	20.5
65	Tb	Terbium	0.131 31^†	12.670
66	Dy	Dysprosium	0.015	1.45
67	Ho	Holmium	0.338	32.61
68	Er	Erbium	0.312	30.10
69	Tm	Thulium	1.029	99
70	Yb	Ytterbium	−0.02	−1.93	est.
71	Lu	Lutetium	0.238 8^†	23.04
72	Hf	Hafnium	0.178 0^†	17.18
73	Ta	Tantalum	0.328 859^†	31.730 1
74	W	Tungsten	0.816 500^†	78.780 3
75	Re	Rhenium	0.060 396^†	5.827 3
76	Os	Osmium	1.077 661^†	103.978 5
77	Ir	Iridium	1.564 057^†	150.908 6
78	Pt	Platinum	2.125 10	205.041
79	Au	Gold	2.308 610	222.747
80	Hg	Mercury	−0.5	−48	est.
81	Tl	Thallium	0.320 053	30.880 4
82	Pb	Lead	0.356 721	34.418 3
83	Bi	Bismuth	0.942 362	90.924
84	Po	Polonium	1.40	136	calc.
85	At	Astatine	2.415 78	233.087
86	Rn	Radon	−0.7	−68	est.
87	Fr	Francium	0.486	46.89	est.
88	Ra	Radium	0.10	9.648 5	est.
89	Ac	Actinium	0.35	33.77	est.
90	Th	Thorium	0.607 69^†	58.633
91	Pa	Protactinium	0.55	53.03	est.
92	U	Uranium	0.314 97^†	30.390
93	Np	Neptunium	0.48	45.85	est.
94	Pu	Plutonium	−0.50	−48.33	est.
95	Am	Americium	0.10	9.93	est.
96	Cm	Curium	0.28	27.17	est.
97	Bk	Berkelium	−1.72	−165.24	est.
98	Cf	Californium	−1.01	−97.31	est.
99	Es	Einsteinium	−0.30	−28.60	est.
100	Fm	Fermium	0.35	33.96	est.
101	Md	Mendelevium	0.98	93.91	est.
102	No	Nobelium	−2.33	−223.22	est.
103	Lr	Lawrencium	−0.31	−30.04	est.
111	Rg	Roentgenium	1.565	151.0	calc.
113	Nh	Nihonium	0.69	66.6	calc.
115	Mc	Moscovium	0.366	35.3	calc.
116	Lv	Livermorium	0.776	74.9	calc.
117	Ts	Tennessine	1.719	165.9	calc.
118	Og	Oganesson	0.080	7.72	calc.
119	Uue	Ununennium	0.662	63.87	calc.
120	Ubn	Unbinilium	0.021	2.03	calc.
121	Ubu	Unbiunium	0.57	55	calc.

Molecules

The electron affinities E_ea of some molecules are given in the table below, from the lightest to the heaviest. Many more have been listed by. The electron affinities of the radicals OH and SH are the most precisely known of all molecular electron affinities.

Second and third electron affinity

Z	Element	Name	Electron affinity	Electron affinity	References
7	N⁻	Nitrogen	−6.98	−673
7	N²⁻	Nitrogen	−11.09	−1070
8	O⁻	Oxygen	−7.71	−744
15	P⁻	Phosphorus	−4.85	−468
15	P²⁻	Phosphorus	−9.18	−886
16	S⁻	Sulfur	−4.73	−456
33	As⁻	Arsenic	−4.51	−435
33	As²⁻	Arsenic	−8.31	−802
34	Se⁻	Selenium	−4.25	−410

Electron affinity (data page)

Elements

Molecules

Second and third electron affinity

Specific molecules