Question

Assertion :In an atom, the velocity of electron in the higher orbit keeps on decreasing. Reason: Velocity of electrons is inversely proportional to radius of the orbit.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Assertion
In an atom, the velocity of electron in the higher orbit keeps on decreasing.
$V_n=2.165\times {10}^6\times \frac{Z}{n}m/s$
With increase in $n$, the value of $V_n$
Reason
Velocity of electrons is inversely proportional to radius of the orbit.
$V_n=2.165\times {10}^6\times \frac{Z}{n}m/s$
But
$r_n=\frac{0.53\times n^2}{Z}$
$\frac{r_n}{0.53\times n}=\frac{n}{Z}$
Hence,
$V_n=2.165\times {10}^6\times \frac{Z}{n}m/s$
$V_n=2.165\times {10}^6\times \frac{0.53\times n}{r_n}m/s$

Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
Hence, the option (B) is the correct answer.