Explanation:
\(T = \frac{{2\pi r}}{v},r = \frac{{{n^2}{h^2}{\varepsilon _0}}}{{\pi mZ{e^2}}}\,\,\,\& \,\,v = \frac{{Z{e^2}}}{{2{\varepsilon _0}nh}}\)
\(T = (2\pi )\frac{{\left( {\frac{{{n^2}{h^2}{\varepsilon _0}}}{{\pi mZ{e^2}}}} \right)}}{{\left( {\frac{{Z{e^2}}}{{2{\varepsilon _0}nh}}} \right)}} \Rightarrow T \propto \frac{{{n^3}}}{{{Z^2}}}\)
