http://www.ck12.org Chapter 3. Chemical Interactions
3.8 Bond Polarity
- Describe polar and nonpolar covalent bonds.
- Explain why some covalent compounds are polar.
Like the north and south poles of a bar magnet, Earth’s north and south magnetic poles—pictured above—are
opposites in terms of their magnetic fields. Some types of chemical bonds and chemical compounds have “poles”
similar to a bar magnet as well. But in the case of chemical bonds and compounds, the poles are opposites in terms
of their electric charge. These bonds and compounds are described as polar.
Polar and Nonpolar Covalent Bonds
Covalent bonds are chemical bonds between atoms of nonmetals that share valence electrons. In some covalent
bonds, electrons are not shared equally between the two atoms. These are calledpolarcovalent bonds. TheFigure
3.13 shows the polar bonds in a water molecule (H 2 O). The oxygen atom attracts the shared electrons more strongly
than the hydrogen atoms do because the nucleus of the oxygen atom has more positively charged protons. As a
result, the oxygen atom becomes slightly negative in charge, and the hydrogen atoms become slightly positive in
charge. For another example of polar bonds, see the video at this URL: http://www.youtube.com/watch?v=1lnjg
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