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，將單個電子結合到電中性的氣態原子或分子上所釋放的能量：

X(g) + e− →  X−(g) + Eea

注意在此定義下，大多數元素原子的電子親和能為正數，即結合電子的過程是放熱的。這裏定義的電子親和能的正負號選取和一般熱力學的定義相反。

在固態物理學之中，對於一表面的電子親合能定義不同。

 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。

週期123456789101112131415161718电子层Ｏ族电子数族I A0173H氢*He氦K2II AIII AIV AV AVI AVII A260Li锂*Be铍27B硼122C碳−7N氮141O氧328F氟*Ne氖LK82353Na钠*Mg镁42Al铝134Si-{zh-hans:硅;zh-hk:硅;zh-tw:矽;}-72P磷200S硫349Cl氯*Ar氩MLK882III BIV BV BVI BVII BVIIII BII B448K钾2Ca钙18Sc钪8Ti钛51V钒65Cr铬0Mn锰15Fe铁64Co钴112Ni镍119Cu铜*Zn锌41Ga镓119Ge锗79As砷195Se硒325Br溴*Kr氪NMLK81882547Rb铷5Sr锶30Y钇41Zr锆86Nb铌72Mo钼53Tc-{zh-cn:锝; zh-tw:鎝; zh-hk:鍀;}-101Ru钌110Rh铑54Pd钯126Ag银*Cd镉39In铟107Sn锡101Sb锑190Te碲295I碘*Xe氙ONMLK8181882646Cs铯14Ba钡镧系*Hf铪31Ta钽79W钨15Re铼104Os锇150Ir铱205Pt铂223Au金*Hg汞36Tl铊35Pb铅91Bi铋190Po钋270At-{zh-hans:砹;zh-hk:砹;zh-tw:砈;}-*Rn氡PONMLK8183218827Fr-{zh-hans:钫;zh-hk:鈁;zh-tw:鍅;}-Ra镭锕系Rf-{zh-cn:𬬻; zh-tw:鑪; zh-hk:鑪;}-Db-{zh-cn:𬭊; zh-tw:𨧀; zh-hk:𨧀;}-Sg-{zh-cn:𬭳; zh-tw:𨭎; zh-hk:𨭎;}-Bh-{zh-cn:𬭛; zh-tw:𨨏; zh-hk:𨨏;}-Hs-{zh-cn:𬭶; zh-tw:𨭆; zh-hk:𨭆;}-Mt-{zh-cn:鿏; zh-tw:䥑; zh-hk:䥑;}-Ds-{zh-cn:𫟼; zh-tw:鐽; zh-hk:鐽;}-Rg-{zh-cn:𬬭; zh-tw:錀; zh-hk:錀;}-Cn-{zh-cn:鿔; zh-tw:鎶; zh-hk:鎶;}-Nh-{zh-cn:鿭; zh-tw:鉨; zh-hk:鉨;}-Fl-{zh-cn:𫓧; zh-tw:鈇; zh-hk:鈇;}-Mc-{zh-cn:镆; zh-tw:鏌; zh-hk:鏌;}-Lv-{zh-cn:𫟷; zh-tw:鉝; zh-hk:鉝;}-Ts鿬Og鿫 镧系元素45La镧92Ce铈Pr镨Nd钕Pm钷Sm钐Eu铕Gd钆Tb铽Dy镝Ho钬Er铒99Tm铥Yb镱33Lu-{zh-hans:镥;zh-hk:鑥;zh-tw:鎦;}-锕系元素Ac锕Th钍Pa镤U铀Np錼Pu鈽Am鋂Cm锔Bk鉳Cf锎Es锿Fm镄Md钔No锘Lr铹

碱金属碱土金属镧系元素锕系元素过渡金属主族金属类金属非金属卤素-{zh-hans:稀有氣體;zh-hk:貴氣體;zh-tw:稀有氣體;}-

 列表及参考资料 
 元素  电子亲合能(kJ/mol)  参考资料 氢  72.77  Pekeris (1962). Lykke, Murray & Lineberger (1991).  氦  -48±20（估计）   锂  59.62  Hotop & Lineberger (1985). Dellwo et al. (1992). Haeffler et al. (1996a).铍-48±20（估计） 硼  26.99  Scheer, Bilodeau & Haugen (1998). 碳  121.78  Scheer et al. (1998a). 氮-6.8 氧  141.004  Hotop & Lineberger (1985). Blondel (1995). Valli, Blondel & Delsart (1999). 氟  328.165  Blondel et al. (1989). Blondel, Delsart & Goldfarb (2001).氖-116±19（估计） 钠  52.87  Hotop & Lineberger (1985) 铝  41.86  Scheer et al. (1998b) 硅  134.07  Scheer et al. (1998a). Blondel, Delsart & Goldfarb (2001). 磷  72.03  Hotop & Lineberger (1985). 硫  200.410  Blondel (1995). 氯  349  Moore (1970). 鉀  48.38  Slater et al. (1978). Andersson et al. (2000). 钙  2.37  Petrunin et al. (1996). 鈧  18(2)  Feigerle, Herman & Lineberger (1981). 钛  8.4(7)  Ilin, Sakharov & Serenkov (1987). 釩  51  Hotop & Lineberger (1985). 鉻  65.2  Bilodeau, Scheer & Haugen (1998). 铁  14.6(3)  Leopold & Lineberger (1986). 鈷  64.0  Scheer et al. (1998c). 鎳  111.6  Scheer et al. (1998c). 銅  119.24  Bilodeau, Scheer & Haugen (1998). 镓  41(3)  Williams et al. (1998a). 锗  118.94  Scheer et al. (1998a). 砷  78.5(7)  Lippa et al. (1998). 硒  194.97  Hotop & Lineberger (1985). Mansour et al. (1988). 溴  342.54  Blondel et al. (1989). 銣  46.89  Frey, Breyer & Hotop (1978). 鍶  5.02  Andersen et al. (1997). 釔  30  Feigerle, Herman & Lineberger (1981). 鋯  41  Hotop & Lineberger (1985). 鈮  86(2)  Hotop & Lineberger (1985). 鉬  72.3  Bilodeau, Scheer & Haugen (1998). 釕  101.0  Norquist et al. (1999). 銠  110.3  Scheer et al. (1998c). 鈀  54.24  Scheer et al. (1998c). 银  125.86  Biladeau, Scheer & Haugen (1998). 銦  39  Williams et al. (1998b). 錫  107.30  Scheer et al. (1998a). 銻  101.06  Scheer, Haugen & Beck (1997). 碲  190.16  Hotop & Lineberger (1985). Haeffler et al. (1996b). 碘  295  Moore (1970). 銫  45.51  Slater et al. (1978). Scheer et al. (1998d). 鋇  13.95  Petrunin et al. (1995). 鑭  45(2)  Covington et al. (1998). 鈰  92(2)  Davis & Thompson (2002a). 銩  99(2)  Davis & Thompson (2002b). 鎦  33  Davis & Thompson (2001). 鉿  0.00  Periodic Table of the Elements(2017) 鉭  31  Hotop & Lineberger (1985). 钨  79  Hotop & Lineberger (1985). Bengali et al. (1992). 鋨  104.0  Biladeau & Haugen (2000). 銥  150.9  Biladeau et al. (1999). 铂  205.04  Biladeau et al. (1999). 金  222.75  Hotop & Lineberger (1985). 鉈  36  Carpenter, Covington & Thompson (2000). 铅  35  Hotop & Lineberger (1985). 鉍  90.92  Biladeau & Haugen (2001). 钋  183.3  砹  270.1 

 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。Remarkable electron accepting properties of the simplest benzenoid cyanocarbons: hexacyanobenzene, octacyanonaphthalene and decacyanoanthracene Xiuhui Zhang, Qianshu Li, Justin B. Ingels, Andrew C. Simmonett, Steven E. Wheeler, Yaoming Xie, R. Bruce King, Henry F. Schaefer III and F. Albert Cotton Chemical Communications, 2006, 758 - 760 Abstract

 列表及参考资料 
 分子 电子亲合能(kJ/mol) 参考资料 雙原子分子   溴分子  244 Janousek & Brauman (1979) 氯氣 227 Janousek & Brauman (1979) 氟氣 297 Janousek & Brauman (1979) 碘分子 246 Janousek & Brauman (1979) 氧氣 43 CRC Handbook 溴化碘 251 Janousek & Brauman (1979) 氯化鋰 59 Janousek & Brauman (1979) 一氧化氮 2 Janousek & Brauman (1979) 三原子分子   二氧化氮 222 Janousek & Brauman (1979) 二氧化硫 105 Janousek & Brauman (1979) 多原子分子   苯 −110 Janousek & Brauman (1979) 1,4-苯二酮 129 CRC Handbook 三氟化硼 255 CRC Handbook 硝酸 59 Janousek & Brauman (1979) 硝基甲烷 38 Janousek & Brauman (1979) 三氯化磷 134 Janousek & Brauman (1979) 六氟化硫 138 CRC Handbook 四氰乙烯 278 CRC Handbook 六氟化鎢 264 CRC Handbook 六氟化鈾 280 CRC Handbook

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

Category:分子物理学
Category:原子物理学
Category:物理化学
Category:化学性质
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