A less talked about part of chemical bonding is Electronegativity. Electronegativity is defined as the ability of an atom in molecule to attract shared electrons to itself. Through experimentation, these values have already been determined. These values can be found in any chemistry book, and these values may be included in some periodic tables. Electronegativity can be used to determine the type of bond by subtracting the electronegativity values for the two atoms. If the difference is zero, the bond is covalent. If the difference is between 0.5 and 2, the bond is polar covalent. In this situation the bond becomes more polar as the value increases until the electrons are ripped from the other. This will make the bond an ionic bond, which has a difference of over 2.     

Remember that Electronegativity increases as you move along the periodic table to the right, and decrease as you go down.

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