Electronegativity & Electronegativity Difference Supplemental Notes Page 4
ADVERTISEMENT
1
2
3
4Electronegativity & Electronegativity Difference Supplemental Notes
Electronegativity Difference
We can use electronegativity to predict and explain the polarity of bonds between pairs of atoms.
The bigger the electronegativity difference the more polar the bond.
0.0 - 0.5
Nonpolar covalent
0.5 - 1.0
Covalent moderately polar
1.0 -1.7
Polar covalent
>1.7
Ionic
For example, the bond between hydrogen and chlorine is a polar covalent bond because chlorine
is more electronegative than hydrogen so chlorine has a stronger pull on the electrons than does
hydrogen. The bond between carbon and oxygen is also a polar covalent bond because oxygen is
more electronegative than carbon. The bond between two hydrogen atoms is a nonpolar covalent
bond because each atom has the same electronegativity. Because the electronegativities of
chlorine and bromine are only slightly different, the bond between them is slightly polar.
Let’s look at how we arrived at these predictions:
Look up the values for hydrogen and chlorine using the electronegativity chart above. H = 2.20
and Cl = 2.83 The difference between the two values = 0.63
C = 2.50 and O = 3.50 The difference between the two values = 1.0
H = 2.20 and H = 2.20 The difference between the two values = 0
1. Using electronegativity difference classify bond type for the following:
a. Cl
b. NaCl
c. HBr
2
Comparing Covalent and Ionic Bonding
Let's push some of these ideas a bit further. By looking at
electronegativity we can talk about gradations in metallic and
nonmetallic character. Although there are many inconsistencies, we can
generalize that metals have low electronegativities (generally below 2)
and nonmetals have high electronegativities (generally above 2). We
can also generalize about ionic and covalent bonding in this way.
Covalent bonding results when there is a small difference in the
electronegativities of the two elements. Ionic bonding results when
there is a very large difference in electronegativities between the two
elements. Some chemists set the dividing line between a small
difference and a large difference at about 1.7 to 1.9. We will use 1.7 as
our dividing line.
If we select pairs of elements, such as those shown here, and compare how different their
electronegativities are, you get a wide range of differences. Consequently, you get a gradation of bond
types. Not just covalent and ionic, but nonpolar covalent, slightly and very polar covalent, slightly ionic
and very ionic. Covalent and ionic bonding can be viewed as extremes on a continuum rather than just
different types of bonds. As differences between electronegativities become larger, the bonds become
more ionic. As the differences become smaller, the bonds become more covalent.
All rights Jim Clark
and Eden Francis
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Education