Class 12 Physics
CBSE and UP Board
Atoms
Chapter-12 Exercise 12.8
NCERT Solutions for Class 12 Physics Chapter 12 Question-8
The radius of the innermost electron orbit of a hydrogen atom is 5.3×10⁻⁻¹¹ m. What are the radii of the n = 2 and n =3 orbits?
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The radius of the innermost orbit of a hydrogen atom, r1 = 5.3 x 10⁻11 m.
Let r2 be the radius of the orbit at n = 2. It is related to the radius of the innermost orbit as:
r2 = (n)²r1
= 4 x 5.3 x 10⁻¹¹ = 2.12 x 10⁻¹⁰ m
For n = 3, we can write the corresponding electron radius as:
r3 = (n)²r1
= 9 x 5.3 x 10⁻¹¹=4.77 x 10⁻10 m
Hence, the radii of an electron for n = 2 and n = 3 orbits are 22.12 x 10⁻¹⁰ m and 4.77 x 10⁻10 m respectively.