Bond Length: Internuclear distance between two adjacent atoms in an species is known as bond length, -Bond length depends on: i) size of the atom involved in the bond formation ii) size of the orbitals involved in the bond formation iii) Lone pair-long pair repulsion iv) Resonance v) s-character of combining orbitals with the increasing size of the atoms and atomic orbitals bond length increases. Lone pair-lone pair repulsion increases bond length (if atoms are small sized) whereas resonance can increase some bond lengths and decrease some other bond length. With increasing s-character bond length decreases, whereas with increasing multiplicity of bonds, bond length decreases. However, in some cases, bond lengths are also affected by relative position of bonds (between two similar atoms). Usually but not always with increasing bond length, bond strength (and hence bond dissociation energy) decreases. In which of the following all bonds are not equivalent?