MHT CET · Physics · Atomic Physics

The radius of hydrogen a tomin its ground state is \(5.3 \times 10^{-11} \mathrm{~m}\). After collision with an electron
it is found to have a radius of \(21.2 \times 10^{-11} \mathrm{~m}\).
What is the prindpal quantum number \(n\) of the final state of atom?

A \(n=4\)
B \(n=2\)
C \(n=16\)
D \(n=3\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(n=2\)

Step-by-step Solution

Detailed explanation

\(r \propto n^{2}\)
ie,
\(
\frac{r_{f}}{r_{i}}=\left(\frac{n_{f}}{n_{i}}\right)^{2}
\)
\(
\begin{array}{l}
\Rightarrow \frac{21.2 \times 10^{-11}}{5.3 \times 10^{-11}}=\left[\frac{n}{1}\right]^{2} \\
\Rightarrow \quad n^{2}=4 \\
\Rightarrow \quad n=2
\end{array}
\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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The radius of hydrogen a tomin its ground state is \(5.3 \times 10^{-11} \mathrm{~m}\). After collision with an electronit is found to have a radius of \(21.2 \times 10^{-11} \mathrm{~m}\).What is the prindpal quantum number \(n\) of the final state of atom?

Step-by-step Solution

The radius of hydrogen a tomin its ground state is \(5.3 \times 10^{-11} \mathrm{~m}\). After collision with an electron
it is found to have a radius of \(21.2 \times 10^{-11} \mathrm{~m}\).
What is the prindpal quantum number \(n\) of the final state of atom?