In a Rutherford scattering experiment when a projectile of charge...

A particle of mass $M_1$ and charge $z_1$ possess initial velocity $u$, when it is at a large distance from the nucleus of an atom having atomic number $\mathrm{z}_2$. At the distance of closest approach, the kinetic energy of particle is completely converted to potential energy. Mathematically, \frac{1}{2} \mathrm{M} }_{1}\m$mathrm{u}^2=\frac{1}{4 \pi \varepsilon_0} \frac{\mathrm{z}_1 \mathrm{z}_2}{\mathrm{r}_0}$ So the energy of the particle is directly proportional to $\mathrm{z}_{1} \mathrm{z}_{2}.$