JEE Main 2025 Jan 28 Shift 2, Chemistry Q16: Bohr's Atomic Model

JEE Main2025Jan 28, Shift 2Chemistry

Which of the following is/are not correct with respect to energy of atomic orbitals of hydrogen atom?

(A) $1 s < 2 p < 3 d < 4 s$

(B) $1 s < 2 s = 2 p < 3 s = 3 p$

(D) $1 s < 2 s < 4 s < 3 d$

Choose the correct answer from the options given below :

A
(B) and (D) only
B
(A) and (C) only
C
(C) and (D) only
D
(A) and (B) only

Solution

For a one-electron species (the hydrogen atom), the orbital energy depends only on the principal quantum number $n$ , not on $l$ . So all orbitals of the same shell are degenerate.

Checking each statement:

(A) $1 s < 2 p < 3 d < 4 s$ : between same- $n$ orbitals it preserves $n$ -ordering ( $n = 1, 2, 3, 4$ ), which is consistent. Correct for H.

(B) $1 s < 2 s = 2 p < 3 s = 3 p$ : correctly shows degeneracy within a shell. Correct for H.

(C) $1 s < 2 s < 2 p < 3 s < 3 p$ : separates $2 s$ from $2 p$ (and $3 s$ from $3 p$ ), which is false for the hydrogen atom because those orbitals are degenerate. Incorrect.

(D) $1 s < 2 s < 4 s < 3 d$ : places $4 s$ below $3 d$ , but in H energy depends only on $n$ , so $3 d < 4 s$ . Incorrect.

$∴$ Statements (C) and (D) are the ones that are not correct.

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JEE Main 2025 Jan 28 Shift 2, Chemistry Q16: Bohr's Atomic Model

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