JEE Main 2025 · 24 January · evening · Single correct · +4 / −1

For hydrogen atom, the orbital/s with lowest energy is/are :
(A) 4 s
(B) 3 pₓ
(C) 3 d_(x²-y²)
(D) 3 d_(z²)
(E) 4 p_z
Choose the correct answer from the options given below :

  1. (a) (A) only
  2. (b) (B) only
  3. (c) (B), (C) and (D) only
  4. (d) (A) and (E) only
Answer and solution

Answer (c) (B), (C) and (D) only

Solution

Chemistry ma’am · 2 steps

Hydrogen has one electron, so energy depends on n alone: every n = 3 orbital ties for lowest here.

  1. One-electron atom. In hydrogen there is no other electron to shield or repel, so the energy of an orbital depends only on the principal quantum number n. The value of l does not matter, so 3s, 3p and 3d all have the same energy.

    Eₙ = -13.6/n² eV

    OrbitalnEnergy (eV)
    (A) 4s4-0.85
    (B) 3pₓ, (C) 3d_(x²-y²), (D) 3d_(z²)3-1.51, lowest
    (E) 4p_z4-0.85
  2. So. The three n = 3 orbitals are degenerate and lower in energy than the n = 4 ones, so the answer is (B), (C) and (D) only, option (c).

The idea to keep. For hydrogen and any one-electron ion, energy depends only on n. The (n + l) rule is for many-electron atoms, where shielding splits the subshells.

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.