4.28

SECTION

4

TABLE 4.4

Electron Affinities of Atoms, Molecules, and Radicals (

Continued

)

C. Radicals (

continued

)

Electron affinity,

Radical

in eV

in kJ · mol

1

CNCH

2 cyanomethyl

1.543(14)

148.9(14)

CO

3

2.69(14)

259.(14)

CS

0.205(21)

19.8(20)

ClO

2.275(6)

219.5(6)

HCO

0.313(5)

30.2(5)

HNO

0.338(15)

32.6(14)

HO

2

1.078(17)

104.0(6)

FO

2.272(6)

219.2(6)

N 3

2.70(12)

260.(12)

NCO

3.609(5)

348.2(5)

NCS

3.537(5)

341.3(5)

NH

0.370(4)

35.7(4)

NO

3

3.937(14)

379.9(14)

NS

1.194(11)

115.2(11)

O 2Aryl

0.52(2)

50.(2)

OClO

2.140(8)

206.5(8)

OH

1.82767(2)

176.343(2)

OIO

2.577(8)

248.6(8)

PH

1.028(10)

99.2(10)

PH

2

1.27(1)

123.(1)

PO

1.092(10)

105.4(10)

PO

2

3.42(1)

330.(1)

SF

2.285(6)

220.5(6)

SH

2.314344(4)

223.300(4)

SO

1.125(5)

108.5(5)

SeH

2.21252(3)

213.475(3)

SiF

3

2.95(10)

285.(10)

SiH

1.277(9)

123.2(9)

SiH

2

1.124(20)

108.4(19)

SiH

3

1.406(14)

106.7(14)

4.4

ELECTRONEGATIVITY

Electronegativity

is the relative attraction of an atom for the valence electrons in a covalent bond.

It is proportional to the

effective nuclear charge and

inversely proportional to the covalent radius:

0.31( n

1

c ) 0.50

r

where

n is the number of valence electrons,

c

is any formal valence charge on the atom and the sign

before it corresponds to the sign of this charge, and

r is the covalent radius. Originally the element

fluorine, whose atoms have the greatest attraction for electrons, was given an arbitrary electroneg-

ativity of 4.0. A revision of Pauling’s values based on newer data assigns

3.90 to fluorine. Values

in Table 4.5 refer to the common oxidation states of the elements.