The bond length is the distance of a bond measured between the nuclei of the two atoms that are bound. It was traditionally expressed in Ångström, in newer approaches this happens in picometer (1 Å = 100 pm). Table Trends
If we look at the halogen sequence HF, H-Cl, H-Br and HI, or the series FF, Cl-Cl, Br-Br and II, then it can be seen that the binding length increases with the size of the binding atoms from which the molecule exists.
If we look at the already C-C, C = C and C≡C, then it is noticeable that the bond length decreases with increasing numbers of bonds between the carbon atoms (binding order).
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