Question

The velocity of the electron in 3rd orbit of hydrogen atom in $cm{s}^{-1}$

• A. ${4.88\times 10}^4$
• B. ${2.44\times 10}^8$
• C. ${7.29\times 10}^7$
• D. ${2.44\times 10}^{12}$

Answer 1

The correct option is C ${7.29\times 10}^7$

For an electron,

$e=4.803\times {10}^{-10}esu$

$m=9.1\times {10}^{-28}g$

$z=1$

Radius of $3rd$ orbit = $r_1\times n^2$ = $0.529\times {10}^{-8}\times 9$

$V_n$ = $[\frac{z{e}^2}{m{r}_n}{]}^{1/2}$

$V_n$ = $7.29\times {10}^{7}cmse{c}^{-1}$

Hence,option C is correct.