电子亲合能

一元素或化合物 X 的电子亲合能（或电子亲和势或电子亲和力） E_ea 等于该物質的 -1 价离子失去一个電子，變成基态原子或化合物時所需吸收的能量。

X⁻ + E_ea → X + e⁻

X 的电子亲合能越大，它夺取电子的能力（或稱「非金属性」）越强，越靠近周期表右侧。氯元素的电子亲合能最大。

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 价离子時放出的能量。此定義下的電子親合能和定義一相同。不過此定義下，放出能量時电子亲和能為正，吸收能量時电子亲和能為負，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 价离子時的能量變化。 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。

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，例如惰性氣體，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，汞和惰氣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。

电子亲合能(週期表)

下列数据以kJ/mole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

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

Po 钋

At 砹

* Rn 氡

P O N M L K

8 18 32 18 8 2

7

Fr 钫

Ra 镭

锕系

Rf 钅卢

Db 钅杜

Sg 钅喜

Bh 钅波

Hs 钅黑

Mt 钅麦

Ds 钅达

Rg 钅仑

Cn 钅哥

Uut

Fl

Uup

Lv

Uus

Uuo

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 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	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).
锂	59.62	Hotop & Lineberger (1985). Dellwo et al. (1992). Haeffler et al. (1996a).
硼	26.99	Scheer, Bilodeau & Haugen (1998).
碳	121.78	Scheer et al. (1998a).
氧	141.004	Hotop & Lineberger (1985). Blondel (1995). Valli, Blondel & Delsart (1999).
氟	328.165	Blondel et al. (1989). Blondel, Delsart & Goldfarb (2001).
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).
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).

分子的电子亲合能

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 hexacyanobenzene C₆(CN)₆ 的電子親合能較富勒烯要高。

列表及参考资料

分子	电子亲合能 (kJ/mol)	参考资料
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
• 电离势
• 电负性
• 价电子

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