Question

The lowest O - O bond length in the following molecule is:
(A)- ${O_2}{F_2}$
(B)- ${O_2}$
(C)- ${H_2}{O_2}$
(D)- ${O_3}$

Answer 1

Hint: Bond length or bond distance is defined as the average distance between the nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent from the rest of the molecule.

Complete step by step answer:
Bond length is related to bond order. In other words when more electrons participate in bond formation the bond will be shorter. Bond length is also inversely related to bond strength and the bond dissociation energy. If all other factors are equal, a stronger bond will be shorter. In case of a bond between two identical atoms, half the bond distance is equal to the covalent radius of any of those atoms. Bond lengths cannot be seen by naked eyes. They are measured in the solid phase by means of X-ray diffraction or approximated in the gas phase by another method known as microwave spectroscopy. A bond between a given pair of atoms may vary for different molecules. For example, the carbon to hydrogen bonds in methane are different from methyl chloride. It is however possible to generalize when the general structure is the same. There are different factors which can affect the bond length. Let's talk about them:
- The bond length gets increased when the size of the atom increases. For example, bond length of H-X (where X if for halogens) are in the order given order:
HI > HBr > HCl > HF.
- The bond length decreases with the multiplicity of the bond i.e. increase in the number of bonds between the same atoms. Hence, bond length of the carbon-carbon bonds are in the following order:
$C \equiv C < C = C < C - C$
- As the s-orbital is smaller in the size, greater will be the s-character and shorter is the hybrid orbital and hence shorter the bond length.
- Polar bond length is generally smaller than the non-polar bond length.

From the above discussion, it is clear that the correct answer of the given question is option (A)- ${O_2}{F_2}$.

Note: Remember that by these methods, we can only find which bond length is longer or shorter between the given sets of molecules and not their actual distance. The actual distance can only be measured by using advanced methods like spectroscopy.