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preface to fifteenth edition

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4.28 SECTION 4<br />

TABLE 4.4<br />

Electron Affinities of A<strong>to</strong>ms, Molecules, and Radicals (Continued)<br />

C. Radicals (continued)<br />

Radical<br />

in eV<br />

Electron affinity,<br />

in kJ · mol 1<br />

CNCH 2 cyanomethyl 1.543(14) 148.9(14)<br />

CO 3 2.69(14) 259.(14)<br />

CS 0.205(21) 19.8(20)<br />

ClO 2.275(6) 219.5(6)<br />

HCO 0.313(5) 30.2(5)<br />

HNO 0.338(15) 32.6(14)<br />

HO 2 1.078(17) 104.0(6)<br />

FO 2.272(6) 219.2(6)<br />

N 3 2.70(12) 260.(12)<br />

NCO 3.609(5) 348.2(5)<br />

NCS 3.537(5) 341.3(5)<br />

NH 0.370(4) 35.7(4)<br />

NO 3 3.937(14) 379.9(14)<br />

NS 1.194(11) 115.2(11)<br />

O 2 Aryl 0.52(2) 50.(2)<br />

OClO 2.140(8) 206.5(8)<br />

OH 1.82767(2) 176.343(2)<br />

OIO 2.577(8) 248.6(8)<br />

PH 1.028(10) 99.2(10)<br />

PH 2 1.27(1) 123.(1)<br />

PO 1.092(10) 105.4(10)<br />

PO 2 3.42(1) 330.(1)<br />

SF 2.285(6) 220.5(6)<br />

SH 2.314344(4) 223.300(4)<br />

SO 1.125(5) 108.5(5)<br />

SeH 2.21252(3) 213.475(3)<br />

SiF 3 2.95(10) 285.(10)<br />

SiH 1.277(9) 123.2(9)<br />

SiH 2 1.124(20) 108.4(19)<br />

SiH 3 1.406(14) 106.7(14)<br />

Source: H. Ho<strong>to</strong>pand W. C. Lineberger, J. Phys. Chem. Reference Data 14:731 (1985).<br />

4.4 ELECTRONEGATIVITY<br />

Electronegativity is the relative attraction of an a<strong>to</strong>m for the valence electrons in a covalent bond.<br />

It is proportional <strong>to</strong> the effective nuclear charge and inversely proportional <strong>to</strong> the covalent radius:<br />

0.31(n 1 c)<br />

0.50<br />

r<br />

where n is the number of valence electrons, c is any formal valence charge on the a<strong>to</strong>m and the sign<br />

before it corresponds <strong>to</strong> the sign of this charge, and r is the covalent radius. Originally the element<br />

fluorine, whose a<strong>to</strong>ms have the greatest attraction for electrons, was given an arbitrary electronegativity<br />

of 4.0. A revision of Pauling’s values based on newer data assigns 3.90 <strong>to</strong> fluorine. Values<br />

in Table 4.5 refer <strong>to</strong> the common oxidation states of the elements.

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