A covalent bond can be characterized by two features: bond length and bond energy.
BOND LENGTH
Bond length is the average distance between the two nuclei of the atoms involved in the bond. As
the number of shared electron pairs increases, the two atoms are pulled closer together, leading to
a decrease in bond length. Thus, for a given pair of atoms, a triple bond is shorter than a double
bond, which is in turn shorter than a single bond.
BOND ENERGY
Bond energy is the energy required to separate two bonded atoms. For a given pair of atoms, the
strength of a bond (and therefore the bond energy) increases as the number of shared electron pairs
increases. So a triple bond is stronger than a double bond, and a double bond is stronger than a
single bond. It is not the case, however, that a double bond is twice as strong (that is, needs twice as
much energy to break) as a single bond. The reason for this will become clearer as we examine
bonding from a slightly different perspective toward the end of this chapter.
BASIC CONCEPT
The larger the bond energy, the harder it is to break the bond, and the stronger the bond.