電子親合能

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，E_ea）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) + E_ea

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。

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。

帶有電子親合能數據的元素週期表

下列數據以kJ/mol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

族

I A

0

1

73 H 氫

* He 氦

K

2

II A

III A

IV A

V A

VI A

VII A

2

60 Li 鋰

* Be 鈹

27 B 硼

122 C 碳

−7 N 氮

141 O 氧

328 F 氟

* Ne 氖

L K

8 2

3

53 Na 鈉

* Mg 鎂

42 Al 鋁

134 Si 硅

72 P 磷

200 S 硫

349 Cl 氯

* Ar 氬

M L K

8 8 2

III B

IV B

V B

VI B

VII B

VIII

I B

II B

4

48 K 鉀

2 Ca 鈣

18 Sc 鈧

8 Ti 鈦

51 V 釩

65 Cr 鉻

0 Mn 錳

15 Fe 鐵

64 Co 鈷

112 Ni 鎳

119 Cu 銅

* Zn 鋅

41 Ga 鎵

119 Ge 鍺

79 As 砷

195 Se 硒

325 Br 溴

* Kr 氪

N M L K

8 18 8 2

5

47 Rb 銣

5 Sr 鍶

30 Y 釔

41 Zr 鋯

86 Nb 鈮

72 Mo 鉬

53 Tc 鍀

101 Ru 釕

110 Rh 銠

54 Pd 鈀

126 Ag 銀

* Cd 鎘

39 In 銦

107 Sn 錫

101 Sb 銻

190 Te 碲

295 I 碘

* Xe 氙

O N M L K

8 18 18 8 2

6

46 Cs 銫

14 Ba 鋇

鑭系

* Hf 鉿

31 Ta 鉭

79 W 鎢

15 Re 錸

104 Os 鋨

150 Ir 銥

205 Pt 鉑

223 Au 金

* Hg 汞

36 Tl 鉈

35 Pb 鉛

91 Bi 鉍

190 Po 釙

270 At 砹

* Rn 氡

P O N M L K

8 18 32 18 8 2

7

Fr 鈁

Ra 鐳

錒系

Rf 鑪

Db 𨧀

Sg 𨭎

Bh 𨨏

Hs 𨭆

Mt 䥑

Ds 鐽

Rg 錀

Cn 鎶

Nh 鉨

Fl 鈇

Mc 鏌

Lv 鉝

Ts 鿬

Og 鿫

鑭系元素

45 La 鑭

92 Ce 鈰

Pr 鐠

Nd 釹

Pm 鉕

Sm 釤

Eu 銪

Gd 釓

Tb 鋱

Dy 鏑

Ho 鈥

Er 鉺

99 Tm 銩

Yb 鐿

33 Lu 鑥

錒系元素

Ac 錒

Th 釷

Pa 鏷

U 鈾

Np 錼

Pu 鈽

Am 鋂

Cm 鋦

Bk 鉳

Cf 鐦

Es 鎄

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	貴氣體

列表及參考資料

元素	電子親合能 (kJ/mol)	參考資料
氫	72.77	Pekeris (1962). Lykke, Murray & Lineberger (1991).
氦	-48±20（估計）
鋰	59.62	Hotop & Lineberger (1985). Dellwo et al. (1992). Haeffler et al. (1996a).
鈹	-48±20（估計）
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（估計）
鈉	52.87	Hotop & Lineberger (1985)
鋁	41.86	Scheer et al. (1998b)
矽	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).
鈣	2.37	Petrunin et al. (1996).
鈧	18(2)	Feigerle, Herman & Lineberger (1981).
鈦	8.4(7)	Ilin, Sakharov & Serenkov (1987).
釩	51	Hotop & Lineberger (1985).
鉻	65.2	Bilodeau, Scheer & Haugen (1998).
鐵	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).
鎵	41(3)	Williams et al. (1998a).
鍺	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).
銀	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).
鎢	79	Hotop & Lineberger (1985). Bengali et al. (1992).
鋨	104.0	Biladeau & Haugen (2000).
銥	150.9	Biladeau et al. (1999).
鉑	205.04	Biladeau et al. (1999).
金	222.75	Hotop & Lineberger (1985).
鉈	36	Carpenter, Covington & Thompson (2000).
鉛	35	Hotop & Lineberger (1985).
鉍	90.92	Biladeau & Haugen (2001).
釙	183.3
砹	270.1

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

分子	電子親合能 (kJ/mol)	參考資料
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

參見

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

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，存於互聯網檔案館）
• Frey, P.; Breyer, F.; Hotop, H. (1978). "High Resolutions Photodetachment from the Rubidium Negative Ion around the Rb(5p_½) 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，存於互聯網檔案館）
• 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 d⁷s^{2 4}F 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 ³P_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，存於互聯網檔案館）, IUPAC 金色書的定義
• Article about Electron Affinity