4.28 |
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SECTION |
4 |
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TABLE 4.4 |
Electron Affinities of Atoms, Molecules, and Radicals ( |
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Continued |
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C. Radicals ( |
continued |
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Electron affinity, |
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Radical |
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in eV |
in kJ · mol |
1 |
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CNCH |
2 cyanomethyl |
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1.543(14) |
148.9(14) |
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CO |
3 |
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2.69(14) |
259.(14) |
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CS |
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0.205(21) |
19.8(20) |
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ClO |
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2.275(6) |
219.5(6) |
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HCO |
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0.313(5) |
30.2(5) |
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HNO |
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0.338(15) |
32.6(14) |
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HO |
2 |
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1.078(17) |
104.0(6) |
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FO |
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2.272(6) |
219.2(6) |
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N 3 |
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2.70(12) |
260.(12) |
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NCO |
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3.609(5) |
348.2(5) |
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NCS |
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3.537(5) |
341.3(5) |
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NH |
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0.370(4) |
35.7(4) |
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NO |
3 |
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3.937(14) |
379.9(14) |
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NS |
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1.194(11) |
115.2(11) |
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O 2Aryl |
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0.52(2) |
50.(2) |
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OClO |
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2.140(8) |
206.5(8) |
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OH |
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1.82767(2) |
176.343(2) |
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OIO |
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2.577(8) |
248.6(8) |
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PH |
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1.028(10) |
99.2(10) |
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PH |
2 |
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1.27(1) |
123.(1) |
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PO |
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1.092(10) |
105.4(10) |
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PO |
2 |
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3.42(1) |
330.(1) |
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SF |
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2.285(6) |
220.5(6) |
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SH |
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2.314344(4) |
223.300(4) |
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SO |
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1.125(5) |
108.5(5) |
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SeH |
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2.21252(3) |
213.475(3) |
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SiF |
3 |
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2.95(10) |
285.(10) |
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SiH |
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1.277(9) |
123.2(9) |
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SiH |
2 |
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1.124(20) |
108.4(19) |
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SiH |
3 |
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1.406(14) |
106.7(14) |
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Source: H. Hotop and W. C. Lineberger, J. Phys. Chem. Reference Data 14 :731 (1985).
4.4 |
ELECTRONEGATIVITY |
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Electronegativity |
is the relative attraction of an atom for the valence electrons in a covalent bond. |
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It is proportional to the |
effective nuclear charge and |
inversely proportional to the covalent radius: |
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0.31( n |
1 |
c ) 0.50 |
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r |
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where |
n is the number of valence electrons, |
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is any formal valence charge on the atom and the sign |
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before it corresponds to the sign of this charge, and |
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r is the covalent radius. Originally the element |
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fluorine, whose atoms have the greatest attraction for electrons, was given an arbitrary electroneg- |
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ativity of 4.0. A revision of Pauling’s values based on newer data assigns |
3.90 to fluorine. Values |
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in Table 4.5 refer to the common oxidation states of the elements. |
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