1. The problem statement, all variables and given/known data In which of the following pairs of bonds is the shorter bond length not followed by the longer bond length? (1) S―O, P―O (2) C≡C, C=C (3) C=O, C=S (4) C―Si, C―S (5) N≡O, N=O 2. Relevant equations Bond length is determined by the bond order (number of bonds) and bond length is also an indicator of bond strength. The stronger the bond, the shorter the bond. The more bonds, the shorter the bonds. 3. The attempt at a solution Choices 2 and 5 can be immediately eliminated since the triple bonds are obviously shorter than the double bonds. I'm having a hard time narrowing down between the remaining choices (1, 2, and 4). How do I go about determining which bonds are shorter or longer? Does it depend on electronegativity? Strength?