Which of the following molecules has the shortest bond length?

• A. N_2
• B. Cl_2
• C. F_2
• D. O_2

Answer: (A)

Verified step by step guidance

1. Recall that bond length is the average distance between the nuclei of two bonded atoms. It depends on the bond order and the size of the atoms involved.
2. Understand that a higher bond order (number of shared electron pairs) generally corresponds to a shorter bond length because more electrons hold the atoms together more tightly.
3. Determine the bond order for each molecule: \( \mathrm{N_2} \) has a triple bond (bond order 3), \( \mathrm{O_2} \) has a double bond (bond order 2), and both \( \mathrm{F_2} \) and \( \mathrm{Cl_2} \) have single bonds (bond order 1).
4. Consider the atomic sizes: smaller atoms tend to have shorter bond lengths. Fluorine atoms are smaller than chlorine atoms, so \( \mathrm{F_2} \) will have a shorter bond length than \( \mathrm{Cl_2} \) despite both having single bonds.
5. Combine the bond order and atomic size information to conclude that \( \mathrm{N_2} \), with the highest bond order and relatively small atoms, will have the shortest bond length among the given molecules.