Other kinds of connecting additionally the future
Most covalent bonds are formed between atoms of differing electronegativity, meaning that the shared electrons are attracted to one atom within the bond more than the other. As a result, the electrons tend to spend more time at one end of the bond than the other. This sets up what is known as a dipole, literally meaning ‘two poles’. One end of the bond is relatively positive (less attraction for electrons), and one end of the bond is relatively negative (more attraction for electrons). If this difference in electron affinity exists across the molecule, then the molecule is said to be polar – meaning that it will have two different, and opposite, partial charges at either end. Water (H2O) is an excellent example of a polar molecule. Electrons are not shared evenly since hydrogen and oxygen have different electronegativities. This creates dipoles in each H-O bond, and these dipoles do not cancel each other out, leaving the water molecule polar overall (Figure 7). (Read more about these bonds in our module Properties of Liquids.)
Figure 7: In panel A, a molecule of water, H2O, is shown with uneven electron sharing resulting in a partial negative charge around the oxygen atom and partial positive charges around the hydrogen atoms.