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 atom (gas phase). (The energy -or electron affinity- is a scalar quantity and the direction of that energy -released- defines a reaction for which the change in energy ΔE is a negative quantity). The electron affinity is also defined in the case of electron capture as E(initial) – E(final) in order to maintain the positive value.^[1] The reverse definition is that the electron affinity is the energy required to remove an electron from a gaseous anion (still a positive quantity, but in which the change in energy ΔE is also a positive quantity). Either convention can be used in practice, but must be consistent in according a scalar, i.e. positive number to the electron affinity.

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, but they invariably autodetach after some time. The listed value in the table corresponds to a selected low-lying metastable state, which may or may not be the lowest energy resonance. For example, in He⁻ there is a metastable state with 0.359 ms lifetime at 19.7 eV above the ground state of He, however there is also a lower energy resonance at 19.4 eV that only has a 10⁻¹³ s lifetime.^[2]

Z	Element	Name	Electron affinity (eV)	Electron affinity (kJ/mol)	References
1	^1H	Hydrogen	0.754 195(19)	72.769(2)	[3]
	^2D	Deuterium	0.754 59(8)	72.807(8)
2	He	Helium	-19.7		1s2s2p ^4P5/2, 350 μs lifetime.[2]
3	Li	Lithium	0.618 049(2)	59.6327(2)	[4]
4	Be	Beryllium	-2.4		1s2s2p^2 ^4P3/2, 43 μs lifetime.[2]
5	B	Boron	0.279 723(24)	26.989(3)	[5]
6	^12C	Carbon	1.262 122 6(11)	121.776 3(1)	[6]
	^13C		1.262 113 6(12)	121.775 5(2)
7	N	Nitrogen	-1.4		2p^4 ^1D, <1 μs lifetime.[2]
8	^16O	Oxygen	1.461 1134(9)	140.9760(1)	[7]
	^17O		1.461 108(4)	140.9755(4)	[8]
	^18O		1.461 105(3)	140.9752(3)
9	F	Fluorine	3.401 1895(25)	328.1649(3)	[9][10]
10	Ne	Neon	-		no metastable states[2]
11	Na	Sodium	0.547 926(25)	52.867(3)	[11]
12	Mg	Magnesium	-		no metastable states[2]
13	Al	Aluminium	0.432 83(5)	41.762(5)	[12]
14	Si	Silicon	1.3895210(7)	134.0684(1)	[7]
15	P	Phosphorus	0.746 609(9)	72.037(1)	[13]
16	^32S	Sulfur	2.077 1040(6)	200.4101(1)	[7]
	^34S		2.077 1044(12)	200.4101(2)	[14]
17	Cl	Chlorine	3.612 724(27)	348.575(3)	[15]
18	Ar	Argon	-11.5		3p^54s4p ^4S3/2, 260 ns lifetime[2]
19	K	Potassium	0.501 459(12)	48.383(2)	[16]
20	Ca	Calcium	0.024 55(10)	2.37(1)	[17]
21	Sc	Scandium	0.188(20)	18(2)	[18]
22	Ti	Titanium	0.084(9)	8(1)	[19]
23	V	Vanadium	0.526(12)	50.8(12)	[20]
24	Cr	Chromium	0.675 84(12)	65.21(2)	[21]
25	Mn	Manganese	-1 (theoretical)		[2]
26	Fe	Iron	0.151(3)	14.6(3)	[22]
27	Co	Cobalt	0.6633(6)	64.00(6)	[23]
28	Ni	Nickel	1.157 16(12)	111.65(2)
29	Cu	Copper	1.235 78(4)	119.235(4)	[21]
30	Zn	Zinc	-		No stable negative ion.[2]
31	Ga	Gallium	0.43(3)	41(3)	[24]
32	Ge	Germanium	1.232 6764(12)	118.9352(2)	[25]
33	As	Arsenic	0.8048(2)	77.65(2)	[26]
34	Se	Selenium	2.020 6046(11)	194.9587(2)	[27]
35	Br	Bromine	3.363 590(3)	324.5371(3)	[9]
36	Kr	Krypton	-		no metastable states[2]
37	Rb	Rubidium	0.485 916(20)	46.884(2)	[28]
38	Sr	Strontium	0.052 06(6)	5.023(6)	[29]
39	Y	Yttrium	0.307(12)	29.6(12)	[18]
40	Zr	Zirconium	0.427(14)	41.2(14)	[20]
41	Nb	Niobium	0.91740(6)	88.516(7)	[30]
42	Mo	Molybdenum	0.7473(3)	72.10(3)	[21]
43	Tc	Technetium	?		May be unstable like Mn.[2]
44	Ru	Ruthenium	1.046 38(25)	100.96(3)	[31]
45	Rh	Rhodium	1.142 89(20)	110.27(2)	[23]
46	Pd	Palladium	0.562 14(12)	54.24(2)
47	Ag	Silver	1.304 47(3)	125.862(3)	[21]
48	Cd	Cadmium	-		No stable negative ion.[2]
49	In	Indium	0.383 92(6)	37.043(6)	[32]
50	Sn	Tin	1.112 070(2)	107.2984(2)	[33]
51	Sb	Antimony	1.047 401(18)	101.059(2)	[34]
52	Te	Tellurium	1.970 876(7)	190.161(1)	[35]
53	I	Iodine	3.059 0463(38)	295.1531(4)	[36]
54	Xe	Xenon	-0.056(10) (theoretical)		[2]
55	Cs	Caesium	0.471 630(25)	45.505(3)	[11][37]
56	Ba	Barium	0.144 62(6)	13.954(6)	[38]
57	La	Lanthanum	0.47(2)	45(2)	[39]
58	Ce	Cerium	0.57(2)	55(2)	[40]
59	Pr	Praseodymium	0.962(24)	93(3)	[2]
60	Nd	Neodymium	0.162 (theoretical)		[41]
61	Pm	Promethium	0.129 (theoretical)
62	Sm	Samarium	0.162 (theoretical)
63	Eu	Europium	0.116(13)	11(1)	[42]
64	Gd	Gadolinium	0.137 (theoretical)		[41]
65	Tb	Terbium	0.436 (theoretical)
66	Dy	Dysprosium	0.352 (theoretical)
67	Ho	Holmium	0.338 (theoretical)
68	Er	Erbium	0.312 (theoretical)
69	Tm	Thulium	1.029(22)	99(3)	[43]
70	Yb	Ytterbium	0.00(3)		[2]
71	Lu	Lutetium	0.346(14)	33.4(15)	[44][45]
72	Hf	Hafnium	0.114 (theoretical)		[2][46]
73	Ta	Tantalum	0.323(12)	31(2)	[20]
74	W	Tungsten	0.816 26(8)	78.76(1)	[47]
75	Re	Rhenium	0.15(10)	14(10)	[48] May be unstable like Mn.[2]
76	Os	Osmium	1.077 80(12)	103.99(2)	[49]
77	Ir	Iridium	1.564 36(15)	150.94(2)	[50]
78	Pt	Platinum	2.125 10(5)	205.041(5)
79	Au	Gold	2.308 610(25)	222.747(3)	[51]
80	Hg	Mercury	-		No stable negative ion.[2]
81	Tl	Thallium	0.377(13)	36.4(14)	[52]
82	Pb	Lead	0.364(8)	35(1)	[53]
83	Bi	Bismuth	0.942 362(13)	90.924(2)	[54]
84	Po	Polonium	1.405(62) (theoretical)	135.5(60) (theoretical)	[55]
85	At	Astatine	2.42(12) (theoretical)	233.1(11) (theoretical)
86	Rn	Radon
87	Fr	Francium	0.491(5) (theoretical)		[56]
88	Ra	Radium
89	Ac	Actinium
90	Th	Thorium
91	Pa	Protactinium
92	U	Uranium
93	Np	Neptunium
94	Pu	Plutonium
95	Am	Americium
96	Cm	Curium
97	Bk	Berkelium
98	Cf	Californium
99	Es	Einsteinium
100	Fm	Fermium
101	Md	Mendelevium
102	No	Nobelium
103	Lr	Lawrencium
104	Rf	Rutherfordium
105	Db	Dubnium
106	Sg	Seaborgium
107	Bh	Bohrium
108	Hs	Hassium
109	Mt	Meitnerium
110	Ds	Darmstadtium
111	Rg	Roentgenium
112	Cn	Copernicium
113	Uut	Ununtrium
114	Fl	Flerovium
115	Uup	Ununpentium
116	Lv	Livermorium
117	Uus	Ununseptium	2.6 or 1.8 (theoretical)		[57]
118	Uuo	Ununoctium	0.056(10) (theoretical)		[58]
119	Uue	Ununennium	0.662 (theoretical)		[56]
120	Ubn	Unbinilium

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	Eea (eV)	Eea (kJ/mol)	References
Diatomics
^16OH	Hydroxyl	1.827 6487(11)	176.341(2)	Goldfarb et al. (2005)
^16OD		1.825 53(4)	176.137(5)	Schulz et al. (1982)
C2	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)
O2	Dioxygen	0.450(2)	43.42(20)	Schiedt & Weinkauf (1995)
^32SH	Sulfhydryl	2.314 7282(17)	223.337(2)	Chaibi et al. (2006)
F2	Difluorine	3.08(10)	297(10)	Janousek & Brauman (1979)
Cl2	Dichlorine	2.35(8)	227(8)	Janousek & Brauman (1979)
Br2	Dibromine	2.53(8)	244(8)	Janousek & Brauman (1979)
I2	Diiodine	2.524(5)	243.5(5)	Zanni et al. (1997)
IBr	Iodine bromide	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)
Triatomics
NO2	Nitrogen dioxide	2.273(5)	219.3(5)	Ervin, Ho & Lineberger (1988)
O3	Ozone	2.1028(25)	202.89(25)	Novick et al. (1979)
SO2	Sulfur dioxide	1.107(8)	106.8(8)	Nimlos & Ellison (1986)
Larger polyatomics
CH2CHO	Vinyloxy	1.8248(+2-6)	176.07(+3-7)	Rienstra-Kiracofe et al. (2002) after Mead et al. (1984)
C6H6	Benzene	-0.70(14)	−68(14)	Ruoff et al. (1995)
C6H4O2	p-Benzoquinone	1.860(5)	179.5(6)	Schiedt & Weinkauf (1999)
BF3	Boron trifluoride	2.65(10)	256(10)	Page & Goode (1969)
HNO3	Nitric acid	0.57(15)	55(14)	Janousek & Brauman (1979)
CH3NO2	Nitromethane	0.172(6)	16.6(6)	Adams et al. (2009)
POCl3	Phosphoryl chloride	1.41(20)	136(20)	Mathur et al. (1976)
SF6	Sulfur hexafluoride	1.03(5)	99.4(49)	Troe, Miller & Viggiano (2012)
C2(CN)4	Tetracyanoethylene	3.17(20)	306(20)	Chowdhury & Kebarle (1986)
WF6	Tungsten hexafluoride	3.5(1)	338(10)	George & Beauchamp (1979)
UF6	Uranium hexafluoride	5.06(20)	488(20)	NIST chemistry webbook after Borshchevskii et al. (1988)
C60	Buckminsterfullerene	2.6835(6)	258.92(6)	Huang et al. (2014)

Bibliography

• Janousek, Bruce K.; Brauman, John I. (1979), "Electron affinities", in Bowers, M. T., Gas Phase Ion Chemistry 2, New York: Academic Press, p. 53.
• Rienstra-Kiracofe, J.C.; Tschumper, G.S.; Schaefer, H.F.; Nandi, S.; Ellison, G.B. (2002), "Atomic and molecular electron affinities: Photoelectron experiments and theoretical computations", Chem. Rev. 102, pp. 231–282.
• Updated values can be found in the NIST chemistry webbook. These values must be taken taken with caution, however, for the Electron affinity determinations tables of this webbook show unexplained differences with respect to the original measurements. For instance the electron affinity of the iodine atom is told to be 3.05900(10) eV according to the most precise measurement, despite the fact the original publication^[36] gives 3.0590463(38) eV.

Specific molecules

• Adams, C.L.; Schneider, H.; Ervin, K.M.; Weber, J.M. (2009), "Low-energy photoelectron imaging spectroscopy of nitromethane anions: Electron affinity, vibrational features, anisotropies, and the dipole-bound state", J. Chem. Phys. 130: 074307, doi:10.1063/1.3076892
• Borshchevskii, A.Ya.; Boltalina, O.V.; Sorokin, I.D.; Sidorov, L.N. (1988), "Thermochemical quantities for gas-phase iron, uranium, and molybdenum fluorides, and their negative ions", J. Chem. Thermodyn. 20 (5): 523, doi:10.1016/0021-9614(88)90080-8
• Chaibi, W.; Delsart, C.; Drag, C.; Blondel, C. (2006), "High precision measurement of the ³²SH electron affinity by laser detachment microscopy", J. Mol. Spectrosc. 239: 11, doi:10.1016/j.jms.2006.05.012
• Chowdhury, S.; Kebarle, P. (1986), "Electron affinities of di- and tetracyanoethylene and cyanobenzenes based on measurements of gas-phase electron-transfer equilibria", J. Am. Chem. Soc. 108: 5453, doi:10.1021/ja00278a014
• Ervin, K.M.; Ho, J.; Lineberger, W.C. (1988), "Ultraviolet photoelectron spectrum of nitrite anion", J. Phys. Chem. 92: 5405, doi:10.1021/j100330a017
• Ervin, K.M.; Lineberger, W.C. (1991), "Photoelectron spectra of C₂^- and C₂H^-", J. Phys. Chem. 95: 1167, doi:10.1021/j100156a026
• George, P.M.; Beauchamp, J.L. (1979), "The electron and fluoride affinities of tungsten hexafluoride by ion cyclotron resonance spectroscopy", Chem. Phys. 36: 345, doi:10.1016/0301-0104(79)85018-1
• Goldfarb, F.; Drag, C.; Chaibi, W.; Kröger, S.; Blondel, C.; Delsart, C. (2005), "Photodetachment microscopy of the P, Q, and R branches of the OH^-(v=0) to OH(v=0) detachment threshold", J. Chem. Phys 122: 014308, doi:10.1063/1.1824904
• Huang, Dao-Ling; Dau, Phuong Diem; Liu, Hong-Tao; Wang, Lai-Sheng (2014), "High-resolution photoelectron imaging of cold C₆₀⁻ anions and accurate determination of the electron affinity of C₆₀", J. Chem. Phys. 140: 224315, doi:10.1063/1.4881421
• Kim, J.B.; Weichman, M.L.; Neumark, D.M. (2015), "Low-lying states of FeO and FeO⁻ by slow photoelectron spectroscopy", Mol. Phys. 113: 2105, doi:10.1080/00268976.2015.1005706
• Mathur, B.P.; Rothe, E.W.; Tang, S.Y.; Reck, G.P. (1976), "Negative ions from phosphorus halides due to cesium charge exchange", J. Chem. Phys. 65: 565, doi:10.1063/1.433109
• Mead, R.D.; Lykke, K.R.; Lineberger, W.C.; Marks, J.; Brauman, J.I. (1984), "Spectroscopy and dynamics of the dipole‐bound state of acetaldehyde enolate", J. Chem. Phys. 81: 4883, doi:10.1063/1.447515
• Miller, T.M.; Leopold, D.G.; Murray, K.K.; Lineberger, W.C. (1986), "Electron affinities of the alkali halides and the structure of their negative ions", J. Chem. Phys. 85: 2368, doi:10.1063/1.451091
• Nimlos, Mark R.; Ellison, G. Barney (1986), "Photoelectron spectroscopy of sulfur-containing anions (SO₂^-, S₃^-, and S₂O^-)", J. Phys. Chem. 90: 2574, doi:10.1021/j100403a007
• Novick, S.E.; Engelking, P.C.; Jones, P.L.; Futrell, J.H.; Lineberger, W.C. (1979), "Laser photoelectron, photodetachment, and photodestruction spectra of O₃⁻", J. Chem. Phys. 70: 2652, doi:10.1063/1.437842
• Page, F. M.; Goode, G. C. (1969), Negative ions and the magnetron, John Wiley & Sons^[59]
• Ruoff, R.S.; Kadish, K.M.; Boulas, P.; Chen, E.C.M. (1995), "Relationship between the Electron Affinities and Half-Wave Reduction Potentials of Fullerenes, Aromatic Hydrocarbons, and Metal Complexes", J. Phys. Chem. 99: 8843, doi:10.1021/j100021a060
• Schiedt, J.; Weinkauf, R. (1995), "Spin-orbit coupling in the O₂^- anion", Z. Naturforsch. A 50 (11): 1041, doi:10.1515/zna-1995-1110
• Schiedt, J.; Weinkauf, R. (1999), "Resonant photodetachment via shape and Feshbach resonances: p-benzoquinone anions as a model system", J. Chem. Phys. 110: 304, doi:10.1063/1.478066
• Schulz, P.A.; Mead, R.D.; Jones, P.L.; Lineberger, W.C. (1982), "OH⁻ and OD⁻ threshold photodetachment", J. Chem. Phys. 77: 1153, doi:10.1063/1.443980
• Sheps, L.; Miller, E.M.; Lineberger, W.C. (2009), "Photoelectron spectroscopy of small IBr⁻(CO₂)_n(n=0–3) cluster anions", J. Chem. Phys. 131: 064304, doi:10.1063/1.3200941
• Travers, M.J.; Cowles, D.C.; Ellison, G.B. (1989), "Reinvestigation of the electron affinities of O₂ and NO", Chem. Phys. Lett. 164: 449, doi:10.1016/0009-2614(89)85237-6
• Troe, J.; Miller, T.M.; Viggiano, A.A. (2012), "Revised electron affinity of SF₆ from kinetic data", J. Chem. Phys. 136: 121102, doi:10.1063/1.3698170
• Wenthold, P.G.; Kim, J.B.; Jonas, K.-L.; Lineberger, W.C. (1997), "An Experimental and Computational Study of the Electron Affinity of Boron Oxide", J. Phys. Chem. A 101: 4472, doi:10.1021/jp970645u
• Zanni, M.T.; Taylor, T.R.; Greenblatt, B.J.; Soep, B.; Neumark, D.M. (1997), "Characterization of the I₂⁻ anion ground state using conventional and femtosecond photoelectron spectroscopy", J. Chem. Phys. 107: 7613, doi:10.1063/1.475110

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See also