电子亲合性

在一般化學與原子物理學中，**電子親合能**（或**電子親和勢**、**電子親和力**，electron affinity，**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 價離子時放出的能量。此定義下的電子親合能和定義一相同。不過此定義下，放出能量時電子親和能為正，吸收能量時電子親和能為負，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 價離子時的**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。

總的來說，同一週期從左至右，價殼層電子遞增，使得原子穩定性上昇，原子半徑遞減，對電子的吸引能力漸強，因而電子親合能遞增；同族元素從上到下，因原子半徑的增大，而且總電子數增加，原子穩定性下降，元素電負性值遞減。
實際上，隨核電荷數遞增或同族元素從上到下，電子親和能的變化並不單調。

### 電子親合能 (週期表)

下列數據以 kJ/mole 為單位。帶星號的元素在量子力學基態被認為有接近零的電子親合能。

### 列表及參考資料

## 分子的電子親合能

電子親合能 _E_ea 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。

### 列表及參考資料

## 參見

* Koopmans' theorem
* One-electron reduction
* 游離能
* 電負性
* 價電子

## 注釋

## 參考資料

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_ （頁面存檔備份，存於網際網路檔案館）
* 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_ （頁面存檔備份，存於網際網路檔案館）
* 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 4_F_ levels in Ru−, including calculated hyperfine structure and _M_1 decay rates". 物理評論 A (Physical Review A) **59**:1896–1902. 1 _摘要_
* Pekeris, C.L. (1962). "1 1_S_, 2 1_S_, and 2 3_S_ 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 3_P_ 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 3_P_J 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_

## 外部連結

* Electron affinity （頁面存檔備份，存於網際網路檔案館）, IUPAC 金色書的定義
* Article about Electron Affinity