Data : z = 1, m = 9.1 × 10-31 kg,
e = 1.6 × 10-19 C,
εo = 8.85 × 10-12 C2 / N.m2 ,
h = 6.63 × 10-34 J.s,
n = 2, t = 10-8 s
The periodic time of the electron in a hydrogen atom,
T = \(\cfrac{4e^2_oh^3n^3}{\pi me^4}\)

Let N be the number of revolutions made by the electron in time t. Then, t = NT.
∴ N = \(\cfrac{t}T\) = \(\cfrac{10^{-8}}{3.898\times10^{-16}}\) = 2.565 x 7