What is electronegativity?
Electronegativity is a measure of an atom's ability to attract the shared electons of a covalent bond to itself. If atoms bonded together have the same electronegativity, the shared electrons will be equally shared. If the electrons are more attracted to one of the atoms (because it is more electronegative), the electrons will be unequally shared. If the difference in electronegativity is large enough, the electrons will not be shared at all; the more electronegative atom will "take" them resulting in two ions and an ionic bond.
There are periodic trends in electronegativity. Fluorine has the highest electronegativity and in general, moving down a column and across a row (to the left) from fluorine electronegativity decreases.
The electronegativity values shown in the table below are relative with fluorine having a value of 4.0.
 VALUES
DECREASE |
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| H 2.1 |
|
V A L U E S D E C R E A S E  |
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| Li 1.0 |
Be 1.5 |
B 2.0 |
C 2.5 |
N 3.0 |
O 3.5 |
F 4.0 |
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| Na 1.0 |
Mg 1.2 |
Al 1.5 |
Si 1.8 |
P 2.1 |
S 2.5 |
Cl 3.0 |
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| K 0.9 |
Ca 1.0 |
Sc 1.3 |
Ti 1.4 |
V 1.5 |
Cr 1.6 |
Mn 1.6 |
Fe 1.7 |
Co 1.7 |
Ni 1.8 |
Cu 1.8 |
Zn 1.6 |
Ga 1.7 |
Ge 1.9 |
As 2.1 |
Se 2.4 |
Br 2.8 |
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| Rb 0.9 |
Sr 1.0 |
Y 1.2 |
Zr 1.3 |
Nb 1.5 |
Mo 1.6 |
Tc 1.7 |
Ru 1.8 |
Rh 1.8 |
Pd 1.8 |
Ag 1.6 |
Cd 1.6 |
In 1.6 |
Sn 1.8 |
Sb 1.9 |
Te 2.1 |
I 2.5 |
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| Cs 0.8 |
Ba 1.0 |
La 1.1 |
Hf 1.3 |
Ta 1.4 |
W 1.5 |
Re 1.7 |
Os 1.9 |
Ir 1.9 |
Pt 1.8 |
Au 1.9 |
Hg 1.7 |
Tl 1.6 |
Pb 1.7 |
Bi 1.8 |
Po 1.9 |
At 2.1 |
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| Fr 0.8 |
Ra 1.0 |
Ac 1.1 |
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