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4.5 Electronegativity
Relative abilities of an atom to draw the bonding electrons towards its nuclei is expressed in terms of electronegativity.
It is a measure of how powerfully a bonded atom attracts the electrons in the bond.
An electronegativity scale has been developed by Linus Pauling to describe
the attraction of the elements in a chemical bond for shared electrons.
|
H
2.2 |
Table 7 The Electronegativity Scale ( H = 2 .2 ) |
|
Li
1 |
Be
1.5 |
Slight difference in these figures have been reported in different
citations
|
B
2.0 |
C
2.5 |
N
3.0 |
O
3.5 |
F
4.0 |
|
Na
0.9 |
Mg
1.2 |
Al
1.5 |
Si
1.8 |
P
2.1 |
S
2.5 |
Cl
3.1 |
|
K
0.8 |
Ca
1.0 |
Ga
1.7 |
Ge
1.8 |
As
2.1 |
Se
2.4 |
Br
3.0 |
|
Rb
0.8 |
Sr
1.0
Ba
0.9 |
|
Sn
1.9 |
Sb
2 |
Te
2.1 |
I
2.6 |
|
Cs
0.7 |
Pb
2.3 |
Bi
2 |
Po
2 |
At
2.2 |
The importance of these quantities lies in the fact that they at least qualitatively reflect the chemical behavior of the elements. The greater the separation between two atoms in the electronegativity scale the greater is the ionic character of a bond between them. The bond between two highly electronegative atoms is covalent as in NO or CCl4. The bond linking two elements of low electronegativity is a metallic one as in Brass (Cu + Zn). The bond type between a highly electronegative and a low electronegative element is ionic as in KCl.
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