Speed of an electron in Bohr’s 7 ^ th orbit for Hydrogen atom...

For hydrogen like atom, the velocity of electron in ${n}^{th}$ orbit is given by

$v = \dfrac{{z}^{2}{e}^{2}}{2{ε}_{0}hn}$

$∴ v ∝ \dfrac{1}{n}$

$⇒ \dfrac{{v}_{1}}{{v}_{2}} = \dfrac{{n}_{2}}{{n}_{1}}$

$⇒ \dfrac{3 . 6 \times {10}^{6}}{{v}_{2}} = \dfrac{3}{7}$

${v}_{2} = 8 . 4 \times {10}^{6}m{s}^{- 1}$