What makes a double bond stronger?

• A. Two pairs of electrons are shared
• B. The atoms have higher atomic numbers
• C. The bond length is longer
• D. The bond is ionic in character

Answer: (A)

The strength of a double bond comes from having two shared pairs of electrons, which raises the bond order to two. This extra shared electron density between the two nuclei increases the electrostatic attraction that holds the atoms together and raises the bond dissociation energy, so more energy is needed to break the bond. Additionally, the stronger attraction pulls the atoms closer, giving a shorter bond length than a single bond, and shorter bonds are generally stronger.

Higher atomic numbers don’t guarantee a stronger covalent bond, since bond strength depends on how the atoms share electrons and how their orbitals overlap, not just how big the atoms are. A longer bond length would indicate a weaker bond, not a stronger one. And if the bond were ionic in character, it would be an electrostatic attraction between ions rather than a covalent sharing of electrons, which is a different type of bond altogether.