Bond length

Bond length is the equilibrium distance between the nuclei of two covalently bonded atoms in a molecule, measured experimentally by X-ray diffraction and electron diffraction techniques. Two factors chiefly determine a bond's length: first, the SIZE of the two bonded atoms — larger atoms, with more inner shielding shells, sit farther apart, so bond length generally INCREASES as atomic size increases (visible, for instance, in the halogen-halogen series F2 144 pm < Cl2 199 pm < Br2 228 pm < I2 267 pm); and second, the bond's MULTIPLICITY — a higher bond order pulls the two nuclei closer together, so bond length DECREASES as multiplicity increases, following the order single > double > triple ($- > = > \equiv$) — for examp …