Chemistry

Problem

Which of the following expressions correctly gives the speed

v_{n}

of an electron in the nth orbit of hydrogen? a)

v_{n}=\dfrac{e^{2}}{2\pi\varepsilon_{0}\hbar}\,\dfrac{1}{n}

v_{n}=\dfrac{e^{2}}{4\pi\varepsilon_{0}\hbar}\,\dfrac{1}{n}

v_{n}=\dfrac{e^{2}}{4\pi\varepsilon_{0}\hbar}\,\dfrac{1}{n^{2}}

v_{n}=\dfrac{e^{2}}{4\pi\varepsilon_{0}h}\,\dfrac{1}{n}