Multiple Bonds (Simplified): Videos & Practice Problems

Single, double, and triple bonds differ in both bond length and the number of electron pairs shared. A single bond is the longest and involves one pair of electrons (2 electrons). A double bond is shorter than a single bond and involves two pairs of electrons (4 electrons). A triple bond is the shortest and involves three pairs of electrons (6 electrons). As the number of shared electron pairs increases, the bond length decreases.

To determine the number of valence electrons shared in a multiple bond, count the number of bonds between the atoms and multiply by 2 (since each bond involves 2 electrons). For example, a single bond shares 2 electrons, a double bond shares 4 electrons, and a triple bond shares 6 electrons. This helps in understanding the electron distribution in the molecule.

Triple bonds are shorter than single bonds because they involve more shared electron pairs, which increases the electrostatic attraction between the bonded atoms. This stronger attraction pulls the atoms closer together, resulting in a shorter bond length. In contrast, single bonds have fewer shared electrons and thus a weaker attraction, leading to a longer bond length.

Bond order, which is the number of shared electron pairs between two atoms, directly affects both bond strength and bond length. Higher bond orders (e.g., double and triple bonds) result in stronger bonds due to increased electron sharing, and shorter bond lengths due to the stronger attraction between the atoms. Conversely, lower bond orders (e.g., single bonds) result in weaker bonds and longer bond lengths.

Multiple bonds significantly influence molecular geometry by affecting bond angles and the overall shape of the molecule. Double and triple bonds create regions of higher electron density, which can repel other electron pairs more strongly, altering bond angles. For example, in ethene (C₂H₄), the double bond between carbon atoms creates a planar structure with bond angles of approximately 120°. Understanding these effects is crucial for predicting and explaining molecular shapes.