Non-Polar and Polar Covalent Bonds

Non-polar and polar covalent bonds

It is important to be able to determine if a molecule is polar or non-polar since the polarity of molecules affects properties such as solubility, melting points and boiling points.

Electronegativity can be used to explain the difference between two types of covalent bonds. Non-polar covalent bonds occur between two identical non-metal atoms, e.g. \(\text{H}_{2}\), \(\text{Cl}_{2}\) and \(\text{O}_{2}\). Because the two atoms have the same electronegativity, the electron pair in the covalent bond is shared equally between them. However, if two different non-metal atoms bond then the shared electron pair will be pulled more strongly by the atom with the higher electronegativity. As a result, a polar covalent bond is formed where one atom will have a slightly negative charge and the other a slightly positive charge.

This slightly positive or slightly negative charge is known as a partial charge. These partial charges are represented using the symbols \({\delta }^{+}\) (slightly positive) and \({\delta }^{-}\) (slightly negative). So, in a molecule such as hydrogen chloride (\(\text{HCl}\)), hydrogen is \(\text{H}^{\delta^{+}}\) and chlorine is \(\text{Cl}^{\delta^{-}}\).

Tip:

The symbol \(\delta\) is read as delta.

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