Question

which of the highlighted chemical bonds in the molecules below is longest? shortest? in between? which highlighted bond requires the highest energy to break? lowest? in between? answer these questions by completing the second and third columns in the table.

Explanation:

• Bond Length: Bond length depends on the size of the atoms involved. The larger the atom, the longer the bond. The atomic size order is \(C < Si < Ge\). So, the \(C - H\) bond (in the first compound) is the shortest (because \(C\) is the smallest atom among \(C\), \(Si\), and \(Ge\)), the \(Si - H\) bond (in the third compound) is of intermediate length, and the \(Ge - H\) bond (in the second compound) is the longest.
• Bond Energy: Bond energy is inversely related to bond length (shorter bonds are stronger). Since \(C - H\) is the shortest bond, it has the highest bond - energy. The \(Ge - H\) bond is the longest, so it has the lowest bond - energy.

Answer:

• Length of highlighted bond: 1 (longest): \(Ge - H\) bond (second compound), 2: \(Si - H\) bond (third compound), 3 (shortest): \(C - H\) bond (first compound).
• Energy of highlighted bond: Highest energy: \(C - H\) bond (first compound), Lowest energy: \(Ge - H\) bond (second compound).