115
TABLE 9-1
Covalent Bond Radii and Energies, and Electronegativities
Element
H— H
B— B
C— C
C=C
C^C
Si— Si
Si=Si
Ge— <3e
Sn — Sn
N— N
N=N
N==N
P— P
P=P
As — As
Sb— Sb
Bi— Bi
O— 0
0=O
S— S
s=s
Se— Se
Se=Se
Te— Te
F— F
Cl— Cl
Br— Br
I— I
Radius (A)
0.30
0.88
0.772
0.667
0.603
1.17
1.07
1.22
1.40
0.70
0.60
0.55
1.10
1.00
1.21
1.41
1.52
0.66
0.55
1.04
0.94
1.17
1.07
1.37
0.64
0.99
1.14
1.33
Bond energy
AH A _ A (kcal/mole)
104.2
62.7
83.1
147
194
42.2
37.6
34.2
38.4
100
226.2
51.3
117
32.1
30.2
25
33.2
50.9
44.0
33.0
36.6
58.0
46.1
36.1
Electronegativity
(e) of element
2.1
2.0
2.5
1.8
1.8
1.8
3.0
2.1
2.0
1.9
1.9
3.5
2.5
2.4
2.1
4.0
3.0
2.8
2.5
These two generalizations mean that to each element there can be assigned a
"covalent bond energy" (A// A -A), which can be used to estimate the strength
of a bond between any two atoms that form a strictly covalent bond. Table 9-1
lists a few of these covalent bond energy assignments. Carbon and iodine form a
purely covalent bond so, by our second generalization, its approximate bond
energy would be
AH C _, =
= i[83.1 + 36.1] = 59.6kcal