电子亲合能

在一般化學與原子物理學中，电子亲合能（或电子亲和势、电子亲和力，，Eea）的定義是，將使一個電子脫離一個氣態的離子或分子所需耗費，或是釋出的能量。

X−(g)  →  X(g) + e−           ΔH=Eea

在固態物理學之中，對於一表面的電子親合能定義不同。

其他定義 

除以上定義（定義一）之外，電子親合能還有兩種定義方式：

定義二和定義一等價，是將一物質的原子或分子獲得一個電子，變成 -1 价离子時放出的能量。此定義下的電子親合能和定義一相同。不過此定義下，放出能量時电子亲和能為正，吸收能量時电子亲和能為負，正負號的使用和一般熱力學的定義恰好相反。

定義三，是將一物質的原子或分子獲得一個電子，變成 -1 价离子時的能量變化。放熱時數值為負，吸熱時數值為正。定義三的正負號使用和一般熱力學的定義相同。但其電子親合能恰為定義一的負值。(此定義為舊版IUPAC定義)

本文採用定義一的電子親合能。

元素的電子親合能 

並非所有的元素的電子親合能均為正，電子親合能為正表示其 -1 價的離子需吸收能量才能變為電中性的原子（早期的教科書寫有些元素，例如稀有氣體，其電子親合能為負，此說法並未被現代的化學家接受）。若其陰離子較不穩定，容易變成原子，則其電子親合能較低。元素中氯的電子親合能最高，汞和稀有氣體等元素的電子親合能都接近零。一般來說，非金屬的電子親合能都比金屬高。

总的来说，同一周期从左至右，價殼層電子递增，使得原子穩定性上昇，原子半径递减，对电子的吸引能力渐强，因而電子親合能递增；同族元素从上到下，因原子半径的增大，而且總電子數增加，原子穩定性下降，元素电负性值递减。
实际上，随核电荷数递增或同族元素从上到下，电子亲和能的变化并不单调。

带有电子亲合能数据的元素周期表 
下列数据以kJ/mol为单位。带星号的元素在量子力学基態被认为有接近零的电子亲合能。

列表及参考资料

分子的电子亲合能 

電子親合能 Eea 的定義也可以延伸到分子。如苯和萘的電子親合能為負值，而蒽
、菲、芘的電子親合能為正值。電腦模擬實驗證實六氰基苯 C6(CN)6 的電子親合能較富勒烯要高。

列表及参考资料

参见 
Koopmans' theorem
One-electron reduction
游離能
电负性
价电子

注釋

参考资料 
以下許多參考資料的文章名稱會連結至參考資料的本文，不過需要訂閱或付費才能閱讀。(摘要)會連結到參考資料的摘要，不需付費即可閱讀。
Andersen, H.H.; Petrunin, V.V.; Kristensen, P.; Andersen, T. (1997). "Structural properties of the negative strontium ion: Binding energy and fine-structure splitting". 物理評論 A (Physical Review A) 55:3247–49. 1 摘要
Andersson, K.T.; Sandstrom, J.; Kiyan, I.Y.; Hanstorp, D.; Pegg, D.J. (2000). "Measurement of the electron affinity of potassium". 物理評論 A (Physical Review A) 62:022503. 摘要
Bengali, A.A.; Casey, S.M.; Cheng, C.-L.; Dick, J.P.; Fenn, T.; Villaalta, P.W.; Leopold, D.G. (1992). "Negative Ion Photoelectron Spectroscopy of Coordinatively Unsaturated Group VI Metal Carbonyls: Cr(CO)3, Mo(CO)3, and W(CO)3". 美國化學會會誌 (Journal of the American Chemical Society) 114:5257–68. ja00039a043.pdf 摘要
Bilodeau, R.C.; Haugen, H.K. (2000). "Experimental studies of Os−: Observation of a bound-bound electric dipole transition in an atomic negative ion". 物理評論快報（Physical Review Letters）85:534–37. 1 摘要
Bilodeau, R.C.; Haugen, H.K. (2001). "Electron affinity of Bi using infrared laser photodetachment threshold spectroscopy". 物理評論 A (Physical Review A) 64:024501. 摘要
Bilodeau, R.C.; Scheer, M.; Haugen, H.K. (1998). "Infrared Laser Photodetachment of Transition Metal Negative Ions: Studies on Cr−, Mo−, Cu−, and Ag−". J. Phys. B: At. Mol. Opt. Phys. 31:3885–91.
Bilodeau, R.C.; Scheer, M.; Haugen, H.K.; Brooks, R.L. (1999). "Near-threshold Laser Spectroscopy of Iridium and Platinum Negative Ions: Electron Affinities and the Threshold Law". 物理評論 A (Physical Review A) 61:012505. 摘要
Blondel, C. (1995). "Recent experimental achievements with negative ions". Phys. Scr. T58:31.
Blondel, C.; Delsart, C.; Goldfarb, F. (2001). "Electron spectrometry at the μeV level and the electron affinities of Si and F". J. Phys. B: At. Mol. Opt. Phys. 34:L281–88.
Blondel, C.; Cacciani, P.; Delsart, C.; Trainham, R. (1989). "High Resolution Determination of the Electron Affinity of Fluorine and Bromine using Crossed Ion and Laser Beams". 物理評論 A (Physical Review A) 40:3698–3701. 1 摘要
Carpenter, D.L.; Covington, A.M.; Thompson J.S. (2000). "Laser Photodetachment Electron Spectroscopy of Tl−". 物理評論 A (Physical Review A) 61:042501. 摘要
Covington, A.M.; Calabrese, D.; Thompson, J.S.; Kvale, T.J. (1998). "Measurement of the electron affinity of lanthanum", J. Phys. B: At. Mol. Opt. Phys. 31:L855–60. 
CRC Handbook of Chemistry and Physics (62nd Edn. (1981); Weast, Robert C. (ed)). Boca Raton, FL: CRC Press. "Section E, General Physical Constants; Electron Affinities".
Davis, V.T.; Thompson, J.S. (2001). "Measurement of the electron affinity of lutetium". J. Phys. B: At. Mol. Opt. Phys. 34:L433–37.
Davis, V.T.; Thompson, J.S. (2002a). "Measurement of the electron affinity of cerium". 物理評論快報（Physical Review Letters）88:073003. 摘要
Davis, V.T.; Thompson, J.S. (2002b). "Measurement of the electron affinity of thulium". Phys. Rev. A 65:010501. 摘要
Dellwo, J.; Liu, Y.; Pegg, D.J.; Alton, G.D. (1992). "Near-Threshold Photodetachment of the Li− Ion". 物理評論 A (Physical Review A) 45:1544–47. 1 摘要
Feigerle, C.S.; Herman, Z.; Lineberger, W.C. (1981). "Laser Photoelectron Spectroscopy of Sc- and Y-: A Determination of the Order of Electron Filling in Transition Metal Anions". J. Electron Spectrosc. Relat. Phenom. 23:441–50. ob=ArticleURL& udi=B6TGC-44CH2G9-5C& user=10& handle=C-WA-A-AW-AW-MsSAYZA-UUW-U-U-AW-U-U-AAZECUVAUW-AAZDUYVEUW-ADBVDZCBU-AW-U& fmt=summary& coverDate=12/31/1981& rdoc=10& orig=browse& srch=#toc#5251#1981#999769996#270874!& cdi=5251&view=c& acct=C000050221& version=1& urlVersion=0& userid=10&md5=9b77fd58e65e977bf40f2096f230307c 摘要 
Frey, P.; Breyer, F.; Hotop, H. (1978). "High Resolutions Photodetachment from the Rubidium Negative Ion around the Rb(5p½) Threshold". J. Phys. B: At. Mol. Opt. Phys. 11:L589–94. 摘要
Haeffler, G.; Hanstorp, G.; Kiyan, I.; Klinkmüller, A.E.; Ljungblad, U.; Pegg, D.J. (1996a). "Electron affinity of Li: A state-selective measurement". 物理評論 A (Physical Review A) 53:4127–31. 1 摘要
Haeffler, G.; Klinkmüller, A.E.; Rangell, J.; Berzinsh, U.; Hanstorp, D. (1996b). "The Electron Affinity of Tellurium". Z. Phys. D 38:211.
Hotop, H.; Lineberger, W.C. (1985). "Binding energies in atomic negative ions. II". J. Phys. Chem. Ref. Data 14:731.
Ilin, R.N.; Sakharov, V.I.; Serenkov, I.T. (1987). "Study of Titanium Negative Ion Using Method of Electron Detachment by an Electric Field". Opt. Spectros. (USSR) 62:578.
Janousek, B. K.; Brauman, J. I. (1979). in Gas Phase Ion Chemistry (Bowers, M. T. (Ed.)), Vol. 2. New York: Academic Press. p. 53.
Leopold, D.G.; Lineberger, W.C. (1986). "A study of the low-lying electronic states of Fe2 and Co2 by negative ion photoelectron spectroscopy". J. Chem. Phys. 85:51–55. 摘要
Lippa, T.P.; Xu, S.J.; Lyapustina, S.A.; Nilles, J.M.; Bowen, K.H. (1998) "Photoelectron spectroscopy of As−, As2−, As3−, As4−, and As5−". J. Chem. Phys. 109:10727–31. 摘要
Lykke, K.R.; Murray, K.K.; Lineberger, W.C. (1991). "Threshold Photodetachment of H−". 物理評論 A (Physical Review A) 43:6104–7. 1 摘要
Mansour, N.B.; Edge, C.J.; Larson, D.J. (1988). "Laser Photodetachment Spectroscopy of Se− and S−". Nucl. Instrum. Meth. Phys. Res. B 31:313–16. ob=ArticleURL& udi=B6TJN-470VCWY-RT& user=10& handle=C-WA-A-ZZ-ZZ-MsSAYVW-UUA-U-U-ZZ-U-U-AAZECUCUZC-AAZDUYCYZC-ADBVYUEYC-ZZ-U& fmt=summary& coverDate=04/02/1988& rdoc=52& orig=browse& srch=#toc#5315#1988#999689998#349206!& cdi=5315&view=c& acct=C000050221& version=1& urlVersion=0& userid=10&md5=6ad26d4a925695cc7a0cd3098b719211 摘要 
Moore, C.E. (1970). National Standard Reference Data Series 34, Washington: National Bureau of Standards, U.S. Government Printing Office.
Norquist, P.L.; Beck, D.R.; Bilodeau, R.C.; Scheer, M.; Srawley, R.A.; Haugen, H.K. (1999). "Theoretical and experimental binding energies for the d7s2 4F levels in Ru−, including calculated hyperfine structure and M1 decay rates". 物理評論 A (Physical Review A) 59:1896–1902. 1 摘要
Pekeris, C.L. (1962). "1 1S, 2 1S, and 2 3S States of H−". 物理評論 (Physical Review ) 126:1470–76. 1 摘要
Petrunin, V.V.; Volstad, J.D.; Balling, P.; Kristensen, K.; Andersen, T. (1995). "Resonant Ionization Spectroscopy of Ba−: Metastable and Stable Ions". 物理評論快報（Physical Review Letters）75:1911–14. 1 摘要
Petrunin, V.V.; Andersen, H.H.; Balling, P.; Andersen, T. (1996). "Structural Properties of the Negative Calcium Ion: Binding Energies and Fine-structure Splitting". 物理評論快報（Physical Review Letters）76:744–47. 1 摘要
Scheer, M.; Bilodeau, R.C.; Haugen, H.K. (1998). "Negative ion of boron: An experimental study of the 3P ground state". 物理評論快報（Physical Review Letters）80:2562–65.
Scheer, M.; Haugen, H.K.; Beck, D.R. (1997). "Single- and Multiphoton Infrared Laser Spectroscopy of Sb−: A Case Study". 物理評論快報（Physical Review Letters）79:4104–7. 1 摘要
Scheer, M.; Bilodeau, R.C.; Brodie, C.A.; Haugen, H.K. (1998a). "Systematic study of the stable states of C−, Si−, Ge−, and Sn− via infrared laser spectroscopy". 物理評論 A (Physical Review A) 58:2844–56. 1 摘要
Scheer, M.; Bilodeau, RC; Thogresen, J.; Haugen, HK (1998b). "Threshold Photodetachment of Al−: Electron Affinity and Fine Structure". 物理評論 A (Physical Review A) 57:R1493–96. 1 摘要
Scheer, M.; Brodie, C.A.; Bilodeau, R.C.; Haugen, H.K. (1998c). "Laser spectroscopic measurements of binding energies and fine-structure splittings of Co−, Ni−, Rh−, and Pd−".物理評論 A (Physical Review A) 58:2051–62. 1 摘要
Scheer, M.; Thøgersen, J.; Bilodeau, R.C.; Brodie, C.A.; Haugen, H.K. (1998d). "Experimental Evidence that the 6s6p 3PJ States of Cs− are Shape Resonances". 物理評論快報（Physical Review Letters）80:684–87. 1 摘要
Slater, J.; Read, F.H.; Novick, S.E.; Lineberger, W.C. (1978). "Alkali Negative Ions. III. Multichannel Photodetachment of Cs− and K−". 物理評論 A (Physical Review A) 17:201–13. 1 摘要
Valli, C.; Blondel, C.; Delsart, C. (1999). "Measuring electron affinities with the photodetachment microscope". 物理評論 A (Physical Review A) 59:3809–15. 1 摘要
Williams, W.W.; Carpenter, D.L.; Covington, A.M.; Koepnick, M.C.; Calabrese, D.; Thompson, J.S. (1998a). "Laser photodetachment electron spectrometry of Ga−". J. Phys. B: At. Mol. Opt. Phys. 31:L341–45. 摘要
Williams, W.W.; Carpenter, D.L.; Covington, A.M.; Thompson, J.S.; Kvale, T.J.; Seely, D.G. (1998b). "Fine-Structure-Resolved Laser Photodetachment Electron Spectroscopy of In−". 物理評論 A (Physical Review A) 58:3582–84. 1 摘要

外部链接 
Electron affinity , IUPAC 金色書的定義
Article about Electron Affinity

分子物理学
原子物理学
物理化学
化学性质
能量
离子