A diatomic molecule has a dipole moment of 1.2D. If its bond length is $1{ \mathrm{A}}^0$, the fraction of electronic charge that exists on each atom is

It is given to find out the fraction of electronic charge that exists on each atom. 

Dipole moment is 1.2D 

The bond length is $1{ \mathrm{A}}^0$, 

The dipole moment is an estimation of the polarity of a molecule. It is the product of the magnitude of the charge and the distance between the charges. 

$$\begin{gathered} \text{ Dipole moment }\left(\mu \right)=\mathrm{charge}\left(\mathrm{q}\right)\times \text{ distance }\left(\mathrm{d}\right) \\ \begin{array}{rl} & \mu =\mathrm{q}\times \mathrm{d}\\ & 1.2\times {10}^{-18}=\mathrm{q}\times {10}^{-8}\mathrm{cm}\\ & \mathrm{q}=\frac{1.2\times {10}^{-18}}{{10}^8}=1.2\times {10}^{-10}\end{array} \\ \text{Charge on each atom}=\frac{\mathrm{q}}{\mathrm{e}}\times 100=\frac{1.2\times {10}^{-10}}{4.8\times {10}^{-10}}\times 100=25\mathrm{\%} \end{gathered}$$

So, option A is correct.