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 called polar covalent bonds. The Figure below 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=1lnjg81daBs.