Atoms And Nuclei Question 71
Question: The radius of hydrogen atom in its ground state is $ 5.3\times {{10}^{-11}}m $ . After collision with an electron it is found to have a radius of $ 21.2\times {{10}^{-11}}m $ . What is the principal quantum number n of the final state of the atom [CBSE PMT 1994; CPMT 2001; MH CET 2000]
Options:
A) n = 4
B) n = 2
C) n = 16
D) n = 3
Show Answer
Answer:
Correct Answer: B
Solution:
$ r\propto n^{2}\ i.e.\frac{r_{f}}{r_{i}}={{( \frac{n_{f}}{n_{i}} )}^{2}} $
Þ $ \frac{21.2\times {{10}^{-11}}}{5.3\times {{10}^{-11}}}={{( \frac{n}{1} )}^{2}} $
Þ $ n^{2}=4 $
Þ n = 2
