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Question: Answered & Verified by Expert
Based on the Bohr's theory of hydrogen atom, the speed of the electron, energy of the electron and the radius of its orbit varies with the principal quantum number, respectively as
ChemistryStructure of AtomTS EAMCETTS EAMCET 2021 (06 Aug Shift 2)
Options:
  • A $n: n^2: n^2$
  • B $\frac{1}{n^2}: \frac{1}{n}: n$
  • C $\frac{1}{n}: \frac{1}{n}: n^2$
  • D $\frac{1}{n}: \frac{1}{n^2}: n^2$
Solution:
2499 Upvotes Verified Answer
The correct answer is: $\frac{1}{n}: \frac{1}{n^2}: n^2$
According to Bohr's theory of hydrogen at
(i) The speed of electron in the $n$th orbit,
$$
\begin{aligned}
v_n & =\frac{1}{n} \frac{e^2}{4 \pi \varepsilon_0(h / 2 \pi)} \\
\text { or, } \quad v_n & \propto \frac{1}{n}
\end{aligned}
$$
(ii) The energy of electron in the $n$th orbit,
$$
\begin{aligned}
E_n & =\frac{m e^4}{8 n^2 \varepsilon_0^2 h^2} \\
\text { or, } E_n & \propto \frac{1}{n^2}
\end{aligned}
$$
(iii) The radius of the electron in $n$th orbit,
$$
r_n=\frac{n^2 h^2 \varepsilon_0}{\pi m e} \quad \text { or } \quad r_n \propto n^2
$$
So, the correct ratio is $1 / n: 1 / n^2: n^2$.

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