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The speed of the electron (in $\mathrm{ms}^{-1}$ ) in the third orbit of hydrogen atom is approximately $\left(\right.$ mass of electron $=9.1 \times 10^{-31} \mathrm{~kg}$ )
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The correct answer is:
$7.26 \times 10^5$
Velocity of an electron can be given as follows:
Velocity (speed) $[v]=2.18 \times 10^6 \cdot \frac{Z}{n}$
where, $Z=$ atomic number
$n=$ number of orbit
For hydrogen atom, $Z=1 \Rightarrow n=3$
Therefore, $v=2.18 \times 10^6 \cdot \frac{Z}{n}=2.18 \times 10^6 \times \frac{1}{3}$
$\begin{aligned} & =0.726 \times 10^6 \mathrm{~ms}^{-1} \\ v & =7.26 \times 10^5 \mathrm{~ms}^{-1}\end{aligned}$
Hence, option (c) is the correct answer.
Velocity (speed) $[v]=2.18 \times 10^6 \cdot \frac{Z}{n}$
where, $Z=$ atomic number
$n=$ number of orbit
For hydrogen atom, $Z=1 \Rightarrow n=3$
Therefore, $v=2.18 \times 10^6 \cdot \frac{Z}{n}=2.18 \times 10^6 \times \frac{1}{3}$
$\begin{aligned} & =0.726 \times 10^6 \mathrm{~ms}^{-1} \\ v & =7.26 \times 10^5 \mathrm{~ms}^{-1}\end{aligned}$
Hence, option (c) is the correct answer.
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