Question

If an $e^{-}$ is revolving in the first bohr orbit of a H atom with a velocity of $2.19\times 10^{8}cm{s}^{-1}$, what will be the velocity of the e- in the third orbit of H atom

• A. $2.19\times 10^{8}cm{s}^{-1}$
• B. $7.3\times 10^{7}cm{s}^{-1}$
• C. $6.57\times 10^{8}cm{s}^{-1}$
• D. $1.09\times 10^{8}cm{s}^{-1}$

Answer 1

Answer: (B)

The velocity of electron in different orbits is given by the following expression:

$V_n=V_o\times \frac{Z}{n}$

Given, for first Bohr orbital of $H$ -atom

$V_0=2.19\times 10^{8}cm{s}^{-1}$

$\therefore$ The velocity of $e^{-}$ in third orbit of $H$ -atom is $(\because n=3)$

or $V_n=2.19\times 10^8\times \frac{1}{3}$

$V_n=0.73\times 10^{8}cm{s}^{-1}$

or $=7.3\times 10^{7}cm{s}^{-1}$