JEE Main 2025 · 2 April · morning · Single correct · +4 / −1

According to Bohr's model of hydrogen atom, which of the following statement is incorrect?

  1. (a) Radius of 4ᵗʰ orbit is four times larger than that of 2ⁿᵈ orbit
  2. (b) Radius of 8ᵗʰ orbit is four times larger than that of 4ᵗʰ orbit
  3. (c) Radius of 6ᵗʰ orbit is three times larger than that of 4ᵗʰ orbit
  4. (d) Radius of 3ʳᵈ orbit is nine times larger than that of 1ˢᵗ orbit
Answer and solution

Answer (c) Radius of 6ᵗʰ orbit is three times larger than that of 4ᵗʰ orbit

Solution

Chemistry ma’am · 2 steps

Bohr radius grows as n², so square the ratio of the two orbit numbers and check each claim.

  1. Radius rule. For hydrogen (Z = 1), Bohr's model gives rₙ = 0.529 n² Å. The radius depends on the square of n.

    r_(n₂)/r_(n₁) = (n₂/n₁)²

    OptionOrbits comparedActual ratioClaimed ratioStatement is
    (a)4th vs 2nd(4/2)² = 44correct
    (b)8th vs 4th(8/4)² = 44correct
    (c)6th vs 4th(6/4)² = 36/16 = 2.253incorrect
    (d)3rd vs 1st(3/1)² = 99correct
  2. So. The 6th orbit is only 2.25 times the 4th, not 3 times. The incorrect statement is (c).

The idea to keep. In Bohr's model r ∝ n²/Z. For any radius comparison, square the ratio of the n values. Do not just divide the orbit numbers.

Answer from the NTA final answer key. Solution by PrepWiser.

Study Atomic Structure

Asked about 170 times in JEE Main since 2020. This question is from 2025.