电子亲合能

在一般化学与原子物理学中，电子亲合能（或电子亲和势、电子亲和力，electron affinity，E_ea）的定义是，将使一个电子脱离一个气态的离子或分子所需耗费，或是释出的能量。

X⁻_(g) → X_(g) + e⁻ ΔH=E_ea

在固体物理学之中，对于一表面的电子亲合能定义不同。

其他定义

除以上定义（定义一）之外，电子亲合能还有两种定义方式：

定义二和定义一等价，是将一物质的原子或分子获得一个电子，变成 -1 价离子时放出的能量。此定义下的电子亲合能和定义一相同。不过此定义下，放出能量时电子亲和能为正，吸收能量时电子亲和能为负，正负号的使用和一般热力学的定义恰好相反。

定义三，是将一物质的原子或分子获得一个电子，变成 -1 价离子时的能量变化。放热时数值为负，吸热时数值为正。定义三的正负号使用和一般热力学的定义相同。但其电子亲合能恰为定义一的负值。(此定义为旧版IUPAC定义)

本文采用定义一的电子亲合能。

元素的电子亲合能

并非所有的元素的电子亲合能均为正，电子亲合能为正表示其 -1 价的离子需吸收能量才能变为电中性的原子（早期的教科书写有些元素，例如稀有气体，其电子亲合能为负，此说法并未被现代的化学家接受）。若其阴离子较不稳定，容易变成原子，则其电子亲合能较低。元素中氯的电子亲合能最高，汞和稀有气体等元素的电子亲合能都接近零。一般来说，非金属的电子亲合能都比金属高。

总的来说，同一周期从左至右，价壳层电子递增，使得原子稳定性上升，原子半径递减，对电子的吸引能力渐强，因而电子亲合能递增；同族元素从上到下，因原子半径的增大，而且总电子数增加，原子稳定性下降，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态被认为有接近零的电子亲合能。

周期

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

电子层

Ｏ族电子数

族

I A

0

1

73 H 氢

* He 氦

K

2

II A

III A

IV A

V A

VI A

VII A

2

60 Li 锂

* Be 铍

27 B 硼

122 C 碳

-7 N 氮

141 O 氧

328 F 氟

* Ne 氖

L K

8 2

3

53 Na 钠

* Mg 镁

42 Al 铝

134 Si 硅

72 P 磷

200 S 硫

349 Cl 氯

* Ar 氩

M L K

8 8 2

III B

IV B

V B

VI B

VII B

VIII

I B

II B

4

48 K 钾

2 Ca 钙

18 Sc 钪

8 Ti 钛

51 V 钒

65 Cr 铬

0 Mn 锰

15 Fe 铁

64 Co 钴

112 Ni 镍

119 Cu 铜

* Zn 锌

41 Ga 镓

119 Ge 锗

79 As 砷

195 Se 硒

325 Br 溴

* Kr 氪

N M L K

8 18 8 2

5

47 Rb 铷

5 Sr 锶

30 Y 钇

41 Zr 锆

86 Nb 铌

72 Mo 钼

53 Tc 锝

101 Ru 钌

110 Rh 铑

54 Pd 钯

126 Ag 银

* Cd 镉

39 In 铟

107 Sn 锡

101 Sb 锑

190 Te 碲

295 I 碘

* Xe 氙

O N M L K

8 18 18 8 2

6

46 Cs 铯

14 Ba 钡

镧系

* Hf 铪

31 Ta 钽

79 W 钨

15 Re 铼

104 Os 锇

150 Ir 铱

205 Pt 铂

223 Au 金

* Hg 汞

36 Tl 铊

35 Pb 铅

91 Bi 铋

190 Po 钋

270 At 砹

* Rn 氡

P O N M L K

8 18 32 18 8 2

7

Fr 钫

Ra 镭

锕系

Rf 𬬻

Db 𬭊

Sg 𬭳

Bh 𬭛

Hs 𬭶

Mt 鿏

Ds 𫟼

Rg 𬬭

Cn 鿔

Nh 鿭

Fl 𫓧

Mc 镆

Lv 𫟷

Ts 鿬

Og 鿫

镧系元素

45 La 镧

92 Ce 铈

Pr 镨

Nd 钕

Pm 钷

Sm 钐

Eu 铕

Gd 钆

Tb 铽

Dy 镝

Ho 钬

Er 铒

99 Tm 铥

Yb 镱

33 Lu 镥

锕系元素

Ac 锕

Th 钍

Pa 镤

U 铀

Np 镎

Pu 钚

Am 镅

Cm 锔

Bk 锫

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	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).
钾	48.38	Slater et al. (1978). Andersson et al. (2000).
钙	2.37	Petrunin et al. (1996).
钪	18(2)	Feigerle, Herman & Lineberger (1981).
钛	8.4(7)	Ilin, Sakharov & Serenkov (1987).
钒	51	Hotop & Lineberger (1985).
铬	65.2	Bilodeau, Scheer & Haugen (1998).
铁	14.6(3)	Leopold & Lineberger (1986).
钴	64.0	Scheer et al. (1998c).
镍	111.6	Scheer et al. (1998c).
铜	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).
铷	46.89	Frey, Breyer & Hotop (1978).
锶	5.02	Andersen et al. (1997).
钇	30	Feigerle, Herman & Lineberger (1981).
锆	41	Hotop & Lineberger (1985).
铌	86(2)	Hotop & Lineberger (1985).
钼	72.3	Bilodeau, Scheer & Haugen (1998).
钌	101.0	Norquist et al. (1999).
铑	110.3	Scheer et al. (1998c).
钯	54.24	Scheer et al. (1998c).
银	125.86	Biladeau, Scheer & Haugen (1998).
铟	39	Williams et al. (1998b).
锡	107.30	Scheer et al. (1998a).
锑	101.06	Scheer, Haugen & Beck (1997).
碲	190.16	Hotop & Lineberger (1985). Haeffler et al. (1996b).
碘	295	Moore (1970).
铯	45.51	Slater et al. (1978). Scheer et al. (1998d).
钡	13.95	Petrunin et al. (1995).
镧	45(2)	Covington et al. (1998).
铈	92(2)	Davis & Thompson (2002a).
铥	99(2)	Davis & Thompson (2002b).
镏	33	Davis & Thompson (2001).
铪	0.00	Periodic Table of the Elements(2017)
钽	31	Hotop & Lineberger (1985).
钨	79	Hotop & Lineberger (1985). Bengali et al. (1992).
锇	104.0	Biladeau & Haugen (2000).
铱	150.9	Biladeau et al. (1999).
铂	205.04	Biladeau et al. (1999).
金	222.75	Hotop & Lineberger (1985).
铊	36	Carpenter, Covington & Thompson (2000).
铅	35	Hotop & Lineberger (1985).
铋	90.92	Biladeau & Haugen (2001).
钋	183.3
砹	270.1

分子的电子亲合能

电子亲合能 E_ea 的定义也可以延伸到分子。如苯和萘的电子亲合能为负值，而蒽 、菲、芘的电子亲合能为正值。电脑模拟实验证实六氰基苯 C₆(CN)₆ 的电子亲合能较富勒烯要高。

列表及参考资料

分子	电子亲合能 (kJ/mol)	参考资料
双原子分子
溴（分子）	244	Janousek & Brauman (1979)
氯气	227	Janousek & Brauman (1979)
氟气	297	Janousek & Brauman (1979)
碘（分子）	246	Janousek & Brauman (1979)
氧气	43	CRC Handbook
溴化碘	251	Janousek & Brauman (1979)
氯化锂	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
六氟化钨	264	CRC Handbook
六氟化铀	280	CRC Handbook

参见

• Koopmans' theorem
• One-electron reduction
• 游离能
• 电负性
• 价电子

参考资料

以下许多参考资料的文章名称会连结至参考资料的本文，不过需要订阅或付费才能阅读。(摘要)会连结到参考资料的摘要，不需付费即可阅读。

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外部链接

• Electron affinity （页面存档备份，存于互联网档案馆）, IUPAC 金色书的定义
• Article about Electron Affinity