verse Bonds

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There is a distinction made between the types of bonds which form as orbitals overlap. The two most important types are sigma bonds and pi bonds. One way in which these bonds differ is in their location with respect to the internuclear axis (a line which connects the nuclei of two bonded atoms)...

In a sigma bond, orbital overlap is always along the intermuclear axis so the bond is centered directly between the two nuclei. Sigma bond formation is illustrated in the examples shown below:

In contrast, a p bond forms from sideways overlap of orbitals. For example, p orbitals on adjacent atoms can overlap as illustrated below:

Notice that the electron density associated with a p bond lies above and below the internuclear axis rather than along it. As a result, a p bond will be weaker than a s-type bond.

Realize that a p bond never occurs alone. The bonded atoms are always also joined by a s bond.

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