The radius of innermost electron orbit of a hydrogen atom is 5.3 x 10-11m. The difference between the radii of n = 3 and n = 2 orbits is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 2.65 x 10-10 m
In the Bohr model the radius of the n-th orbit of hydrogen is proportional to the square of n, with the innermost radius \( r_1 = 5.3\times10^{-11} \) m.
\( r_n = n^{2} r_1 \)
\( r_3 = 9 \times 5.3\times10^{-11}\,\mathrm{m} = 4.77\times10^{-10}\,\mathrm{m} \)
\( r_2 = 4 \times 5.3\times10^{-11}\,\mathrm{m} = 2.12\times10^{-10}\,\mathrm{m} \)
\( r_3 - r_2 = (9 - 4) \times 5.3\times10^{-11}\,\mathrm{m} = 2.65\times10^{-10}\,\mathrm{m} \)
Note: This question is from NCERT (2026-27). NTA sets numerical questions from NCERT too, so do not ignore NCERT while practising numericals.
NCERT (2026-27):
Exercises – …
