# Electron affinity (data page)

This page deals with the electron affinity as a property of isolated atoms or molecules (i.e. in the gas phase). 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 (reverse) 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 (eV) | Electron affinity (kJ/mol) | References |
| 1 | $^1$H | Hydrogen | 0.754 195(19) | 72.769(2) | |
| 1 | $^2$H | Deuterium | 0.754 67(4) | 72.814(4) | |
| 2 | He | Helium | −0.5(2) | −48(20) | est. |
| 3 | Li | Lithium | 0.618 049(22) | 59.632 6(21) | |
| 4 | Be | Beryllium | −0.5(2) | −48(20) | est. |
| 5 | B | Boron | 0.279 723(25) | 26.989(3) | |
| 6 | $^{12}$C | Carbon | 1.262 122 6(11) | 121.776 3(1) | |
| 6 | $^{13}$C | Carbon | 1.262 113 6(12) | 121.775 5(2) | |
| 7 | N | Nitrogen | −0.07 | −6.8 | |
| 8 | $^{16}$O | Oxygen | 1.461 112 97(9) | 140.975 970(9) | |
| 8 | $^{17}$O | Oxygen | 1.461 108(4) | 140.975 5(3) | |
| 8 | $^{18}$O | Oxygen | 1.461 105(3) | 140.975 2(3) | |
| 9 | F | Fluorine | 3.401 189 8(24) | 328.164 9(3) | |
| 10 | Ne | Neon | −1.2(2) | −116(19) | est. |
| 11 | Na | Sodium | 0.547 926(25) | 52.867(3) | |
| 12 | Mg | Magnesium | −0.4(2) | −40(19) | est. |
| 13 | Al | Aluminium | 0.432 83(5) | 41.762(5) | |
| 14 | Si | Silicon | 1.389 521 2(8) | 134.068 4(1) | |
| 15 | P | Phosphorus | 0.746 609(11) | 72.037(1) | |
| 16 | $^{32}$S | Sulfur | 2.077 104 2(6) | 200.410 1(1) | |
| 16 | $^{34}$S | Sulfur | 2.077 104 5(12) | 200.410 1(2) | |
| 17 | Cl | Chlorine | 3.612 725(28) | 348.575(3) | |
| 18 | Ar | Argon | −1.0(2) | −96(20) | est. |
| 19 | K | Potassium | 0.501 459(13) | 48.383(2) | |
| 20 | Ca | Calcium | 0.024 55(10) | 2.37(1) | |
| 21 | Sc | Scandium | 0.179 380(23)$^†$ | 17.307 6(22) | |
| 22 | Ti | Titanium | 0.075 54(5)$^†$ | 7.289(5) | |
| 23 | V | Vanadium | 0.527 66(20)$^†$ | 50.911(20) | |
| 24 | Cr | Chromium | 0.675 928(27)$^†$ | 65.217 2(26) | |
| 25 | Mn | Manganese | −0.5(2) | −50(19) | est. |
| 26 | Fe | Iron | 0.153 236(35)$^†$ | 14.785(4) | |
| 27 | Co | Cobalt | 0.662 255(47)$^†$ | 63.897 9(45) | |
| 28 | Ni | Nickel | 1.157 16(12) | 111.65(2) | |
| 29 | Cu | Copper | 1.235 78(4) | 119.235(4) | |
| 30 | Zn | Zinc | −0.6(2) | −58(20) | est. |
| 31 | Ga | Gallium | 0.301 166(15)$^†$ | 29.058 1(15) | |
| 32 | Ge | Germanium | 1.232 676 4(13) | 118.935 2(2) | |
| 33 | $^{75}$As | Arsenic | 0.804 486(3) | 77.621 1(3) | |
| 34 | Se | Selenium | 2.020 604 7(12) | 194.958 7(2) | |
| 35 | Br | Bromine | 3.363 588(3) | 324.536 9(3) | |
| 36 | Kr | Krypton | −1.0(2) | −96(20) | est. |
| 37 | Rb | Rubidium | 0.485 916(21) | 46.884(3) | |
| 38 | Sr | Strontium | 0.052 06(6) | 5.023(6) | |
| 39 | Y | Yttrium | 0.311 29(22)$^†$ | 30.035(21) | |
| 40 | Zr | Zirconium | 0.433 28(9)$^†$ | 41.806(9) | |
| 41 | Nb | Niobium | 0.917 40(7)$^†$ | 88.516(7) | |
| 42 | Mo | Molybdenum | 0.747 23(8)$^†$ | 72.097(8) | |
| 43 | Tc | Technetium | 0.55(20) | 53(20) | est. |
| 44 | Ru | Ruthenium | 1.046 27(2)$^†$ | 100.950(3) | |
| 45 | Rh | Rhodium | 1.142 89(20) | 110.27(2) | |
| 46 | Pd | Palladium | 0.562 14(12) | 54.24(2) | |
| 47 | Ag | Silver | 1.304 47(3) | 125.862(3) | |
| 48 | Cd | Cadmium | −0.7(2) | −68(20) | est. |
| 49 | In | Indium | 0.383 92(6) | 37.043(6) | |
| 50 | Sn | Tin | 1.112 070(2) | 107.298 4(3) | |
| 51 | Sb | Antimony | 1.047 401(19) | 101.059(2) | |
| 52 | Te | Tellurium | 1.970 875(7) | 190.161(1) | |
| 53 | $^{127}$I | Iodine | 3.059 046 5(37) | 295.153 1(4) | |
| 53 | $^{128}$I | Iodine | 3.059 052(38) | 295.154(4) | |
| 54 | Xe | Xenon | −0.8(2) | −77(20) | est. |
| 55 | Cs | Caesium | 0.4715983(38) | 45.5023(4) | |
| 56 | Ba | Barium | 0.144 62(6) | 13.954(6) | |
| 57 | La | Lanthanum | 0.557 546(20)$^†$ | 53.795(2) | |
| 58 | Ce | Cerium | 0.600 160(27)$^†$ | 57.906 7(26) | |
| 59 | Pr | Praseodymium | 0.109 23(46)$^†$ | 10.539(45) | |
| 60 | Nd | Neodymium | 0.097 49(33)$^†$ | 9.406(32) | |
| 61 | Pm | Promethium | 0.129 | 12.45 | |
| 62 | Sm | Samarium | 0.162 | 15.63 | |
| 63 | Eu | Europium | 0.116(13) | 11.2(13) | |
| 64 | Gd | Gadolinium | 0.212(30)$^†$ | 20.5(29) | |
| 65 | Tb | Terbium | 0.131 31(80)$^†$ | 12.670(77) | |
| 66 | Dy | Dysprosium | 0.015(3) | 1.45(30) | |
| 67 | Ho | Holmium | 0.338 | 32.61 | |
| 68 | Er | Erbium | 0.312 | 30.10 | |
| 69 | Tm | Thulium | 1.029(22) | 99(3) | |
| 70 | Yb | Ytterbium | −0.02 | −1.93 | est. |
| 71 | Lu | Lutetium | 0.238 8(7)$^†$ | 23.04(7) | |
| 72 | Hf | Hafnium | 0.178 0(7)$^†$ | 17.18(7) | |
| 73 | Ta | Tantalum | 0.328 859(23)$^†$ | 31.730 1(22) | |
| 74 | W | Tungsten | 0.816 500(82)$^†$ | 78.780 3(80) | |
| 75 | Re | Rhenium | 0.060 396(64)$^†$ | 5.827 3(62) | |
| 76 | Os | Osmium | 1.077 661(24)$^†$ | 103.978 5(24) | |
| 77 | Ir | Iridium | 1.564 057(12)$^†$ | 150.908 6(12) | |
| 78 | Pt | Platinum | 2.125 10(5) | 205.041(5) | |
| 79 | Au | Gold | 2.308 610(25) | 222.747(3) | |
| 80 | Hg | Mercury | −0.5(2) | −48(20) | est. |
| 81 | Tl | Thallium | 0.320 053(19) | 30.880 4(19) | |
| 82 | Pb | Lead | 0.356 721(2) | 34.418 3(3) | |
| 83 | Bi | Bismuth | 0.942 362(13) | 90.924(2) | |
| 84 | Po | Polonium | 1.40(7) | 136(7) | calc. |
| 85 | At | Astatine | 2.415 78(7) | 233.087(8) | |
| 86 | Rn | Radon | −0.7(2) | −68(20) | 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(6)$^†$ | 58.633(6) | |
| 91 | Pa | Protactinium | 0.55 | 53.03 | est. |
| 92 | U | Uranium | 0.314 97(9)$^†$ | 30.390(9) | |
| 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(6) | 7.72(58) | 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 Rienstra-Kiracofe et al. (2002). The electron affinities of the radicals OH and SH are the most precisely known of all molecular electron affinities.
| Molecule | Name | E$_{ea}$ (eV) | E$_{ea}$ (kJ/mol) | References |
| Diatomics |||||
| $^{16}$OH | Hydroxyl | 1.827 6488(11) | 176.3413(2) | Goldfarb et al. (2005) |
| $^{16}$OD | | 1.825 53(4) | 176.137(5) | Schulz et al. (1982) |
| C$_2$ | Dicarbon | 3.269(6) | 315.4(6) | Ervin & Lineberger (1991) |
| BO | Boron oxide | 2.508(8) | 242.0(8) | Wenthold et al. (1997) |
| NO | Nitric oxide | 0.026(5) | 2.5(5) | Travers, Cowles & Ellison (1989) |
| O$_2$ | Dioxygen | 0.450(2) | 43.42(20) | Schiedt & Weinkauf (1995) |
| $^{32}$SH | Sulfhydryl | 2.314 7283(17) | 223.3373(2) | Chaibi et al. (2006) |
| F$_2$ | Difluorine | 3.08(10) | 297(10) | Janousek & Brauman (1979) |
| Cl$_2$ | Dichlorine | 2.35(8) | 227(8) | Janousek & Brauman (1979) |
| Br$_2$ | Dibromine | 2.53(8) | 244(8) | Janousek & Brauman (1979) |
| I$_2$ | Diiodine | 2.524(5) | 243.5(5) | Zanni et al. (1997) |
| IBr | Iodine monobromide | 2.512(3) | 242.4(4) | Sheps, Miller & Lineberger (2009) |
| LiCl | Lithium chloride | 0.593(10) | 57.2(10) | Miller et al. (1986) |
| FeO | Iron(II) oxide | 1.4950(5) | 144.25(6) | Kim, Weichman & Neumark (2015) |
| CN | Cyano radical | 3.862(4) | 372.6263 | |
| Triatomics |||||
| NO$_2$ | Nitrogen dioxide | 2.273(5) | 219.3(5) | Ervin, Ho & Lineberger (1988) |
| O$_3$ | Ozone | 2.1028(25) | 202.89(25) | Novick et al. (1979) |
| SO$_2$ | Sulfur dioxide | 1.107(8) | 106.8(8) | Nimlos & Ellison (1986) |
| Larger polyatomics |||||
| CH$_2$CHO | Vinyloxy | 1.8248(+2-6) | 176.07(+3-7) | Rienstra-Kiracofe et al. (2002) after Mead et al. (1984) |
| C$_6$H$_6$ | Benzene | −0.70(14) | −68(14) | Ruoff et al. (1995) |
| C$_6$H$_4$O$_2$ | p-Benzoquinone | 1.860(5) | 179.5(6) | Schiedt & Weinkauf (1999) |
| BF$_3$ | Boron trifluoride | 2.65(10) | 256(10) | Page & Goode (1969) |
| HNO$_3$ | Nitric acid | 0.57(15) | 55(14) | Janousek & Brauman (1979) |
| CH$_3$NO$_2$ | Nitromethane | 0.172(6) | 16.6(6) | Adams et al. (2009) |
| POCl$_3$ | Phosphoryl chloride | 1.41(20) | 136(20) | Mathur et al. (1976) |
| SF$_6$ | Sulfur hexafluoride | 1.03(5) | 99.4(49) | Troe, Miller & Viggiano (2012) |
| C$_2$(CN)$_4$ | Tetracyanoethylene | 3.17(20) | 306(20) | Chowdhury & Kebarle (1986) |
| WF$_6$ | Tungsten hexafluoride | 3.5(1) | 338(10) | George & Beauchamp (1979) |
| UF$_6$ | Uranium hexafluoride | 5.06(20) | 488(20) | NIST chemistry webbook after Borshchevskii et al. (1988) |
| C$_{60}$ | Buckminsterfullerene | 2.6835(6) | 258.92(6) | Huang et al. (2014) |

## Second and third electron affinity

| Z | Element | Name | Electron affinity (eV) | Electron affinity (kJ/mol) |
| 7 | N$^−$ | Nitrogen | -6.98 | -673 |
| 7 | N$^{2−}$ | Nitrogen | -11.09 | -1070 |
| 8 | O$^−$ | Oxygen | -7.71 | -744 |
| 15 | P$^−$ | Phosphorus | -4.85 | -468 |
| 15 | P$^{2−}$ | Phosphorus | -9.18 | -886 |
| 16 | S$^−$ | Sulfur | -4.73 | -456 |
| 33 | As$^−$ | Arsenic | -4.51 | -435 |
| 33 | As$^{2−}$ | Arsenic | -8.31 | -802 |
| 34 | Se$^−$ | Selenium | -4.25 | -410 |