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，，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 Xg 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。這裡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。 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。 帶有電子親合能資料的元素週期表 下列資料以 kJmol 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。 週期 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 電子層 Ｏ族電子數 電子層 Ｏ族電子數 族 I A 0 電子層 Ｏ族電子數 1 73H 氫 He 氦 K 2 1 73H 氫 II A III A IV A V A VI A VII A He 氦 K 2 2 60Li 鋰 Be 鈹 27B 硼 122C 碳 7N 氮 141O 氧 328F 氟 Ne 氖 LK 82 3 53Na 鈉 Mg 鎂 42Al 鋁 134Sizhhans 矽；zhhk 矽；zhtw 矽； 72P 磷 200S 硫 349Cl 氯 Ar 氬 MLK 882 3 53Na 鈉 Mg 鎂 III B IV B V B VI B VII B VIII VIII VIII I B II B 42Al 鋁 134Sizhhans 矽；zhhk 矽；zhtw 矽； 72P 磷 200S 硫 349Cl 氯 Ar 氬 MLK 882 4 48K 鉀 2Ca 鈣 18Sc 鈧 8Ti 鈦 51V 釩 65Cr 鉻 0Mn 錳 15Fe 鐵 64Co 鈷 112Ni 鎳 119Cu 銅 Zn 鋅 41Ga 鎵 119Ge 鍺 79As 砷 195Se 硒 325Br 溴 Kr 氪 NMLK 81882 5 47Rb 銣 5Sr 鍶 30Y 釔 41Zr 鋯 86Nb 鈮 72Mo 鉬 53Tczhcn 鎝；zhtw 鎝；zhhk 鎝； 101Ru 釕 110Rh 銠 54Pd 鈀 126Ag 銀 Cd 鎘 39In 銦 107Sn 錫 101Sb 銻 190Te 碲 295I 碘 Xe 氙 ONMLK 8181882 6 46Cs 銫 14Ba 鋇 鑭系 Hf 鉿 31Ta 鉭 79W 鎢 15Re 錸 104Os 鋨 150Ir 銥 205Pt 鉑 223Au 金 Hg 汞 36Tl 鉈 35Pb 鉛 91Bi 鉍 190Po 釙 270Atzhhans 砈；zhhk 砈；zhtw 砈； Rn 氡 PONMLK 818321882 7 Frzhhans 鍅；zhhk 鍅；zhtw 鍅； Ra 鐳 錒系 Rfzhcn鑪 zhtw 鑪；zhhk 鑪； Dbzhcn𨧀 zhtw𨧀 zhhk𨧀 Sgzhcn𨭎 zhtw𨭎 zhhk𨭎 Bhzhcn𨨏 zhtw𨨏 zhhk𨨏 Hszhcn𨭆 zhtw𨭆 zhhk𨭆 Mtzhcn 䥑；zhtw 䥑；zhhk 䥑； Dszhcn鐽 zhtw 鐽；zhhk 鐽； Rgzhcn錀 zhtw 錀；zhhk 錀； Cnzhcn 鎶；zhtw 鎶；zhhk 鎶； Nhzhcn 鿭；zhtw 鉨；zhhk 鉨； Flzhcn鈇 zhtw 鈇；zhhk 鈇； Mczhcn 鏌；zhtw 鏌；zhhk 鏌； Lvzhcn鉝 zhtw 鉝；zhhk 鉝； Ts 鿬 Og 鿫 鑭系元素 鑭系元素 鑭系元素 45La 鑭 92Ce 鈰 Pr 鐠 Nd 釹 Pm 鉕 Sm 釤 Eu 銪 Gd 釓 Tb 鋱 Dy 鏑 Ho 鈥 Er 鉺 99Tm 銩 Yb 鐿 33Luzhhans 鎦；zhhk 鎦；zhtw 鎦； 錒系元素 錒系元素 錒系元素 Ac 錒 Th 釷 Pa 鏷 U 鈾 Np 錼 Pu 鈽 Am 鋂 Cm 鋦 Bk 鉳 Cf 鉲 Es 鑀 Fm 鐨 Md 鍆 No 鍩 Lr 鐒 鹼金屬 鹼土金屬 鑭系元素 錒系元素 過渡金屬 主族金屬 類金屬 非金屬 鹵素 zhhans 稀有氣體；zhhk 貴氣體；zhtw 稀有氣體； 列表及參考資料 元素 電子親合能 kJmol 參考資料 氫 7277 Pekeris 1962 Lykke Murray Lineberger 1991 氦 4820（估計） 鋰 5962 Hotop Lineberger 1985 Dellwo et al 1992 Haeffler et al 1996a 鈹 4820（估計） 硼 2699 Scheer Bilodeau Haugen 1998 碳 12178 Scheer et al 1998a 氮 68 氧 141004 Hotop Lineberger 1985 Blondel 1995 Valli Blondel Delsart 1999 氟 328165 Blondel et al 1989 Blondel Delsart Goldfarb 2001 氖 11619（估計） 鈉 5287 Hotop Lineberger 1985 鋁 4186 Scheer et al 1998b 矽 13407 Scheer et al 1998a Blondel Delsart Goldfarb 2001 磷 7203 Hotop Lineberger 1985 硫 200410 Blondel 1995 氯 349 Moore 1970 鉀 4838 Slater et al 1978 Andersson et al 2000 鈣 237 Petrunin et al 1996 鈧 18 2 Feigerle Herman Lineberger 1981 鈦 84 7 Ilin Sakharov Serenkov 1987 釩 51 Hotop Lineberger 1985 鉻 652 Bilodeau Scheer Haugen 1998 鐵 146 3 Leopold Lineberger 1986 鈷 640 Scheer et al 1998c 鎳 1116 Scheer et al 1998c 銅 11924 Bilodeau Scheer Haugen 1998 鎵 41 3 Williams et al 1998a 鍺 11894 Scheer et al 1998a 砷 785 7 Lippa et al 1998 硒 19497 Hotop Lineberger 1985 Mansour et al 1988 溴 34254 Blondel et al 1989 銣 4689 Frey Breyer Hotop 1978 鍶 502 Andersen et al 1997 釔 30 Feigerle Herman Lineberger 1981 鋯 41 Hotop Lineberger 1985 鈮 86 2 Hotop Lineberger 1985 鉬 723 Bilodeau Scheer Haugen 1998 釕 1010 Norquist et al 1999 銠 1103 Scheer et al 1998c 鈀 5424 Scheer et al 1998c 銀 12586 Biladeau Scheer Haugen 1998 銦 39 Williams et al 1998b 錫 10730 Scheer et al 1998a 銻 10106 Scheer Haugen Beck 1997 碲 19016 Hotop Lineberger 1985 Haeffler et al 1996b 碘 295 Moore 1970 銫 4551 Slater et al 1978 Scheer et al 1998d 鋇 1395 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 000 Periodic Table of the Elements 2017 鉭 31 Hotop Lineberger 1985 鎢 79 Hotop Lineberger 1985 Bengali et al 1992 鋨 1040 Biladeau Haugen 2000 銥 1509 Biladeau et al 1999 鉑 20504 Biladeau et al 1999 金 22275 Hotop Lineberger 1985 鉈 36 Carpenter Covington Thompson 2000 鉛 35 Hotop Lineberger 1985 鉍 9092 Biladeau Haugen 2001 釙 1833 砈 2701 分子的電子親合能 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 列表及參考資料 分子 電子親合能 kJmol 參考資料 雙原子分子 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 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 多原子分子 苯 110 Janousek Brauman 1979 14 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 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