Which of the following is correct set of 4 quantum number of $19^{\text{th}}$ electron in Chromium (Atomic number $=24$) in accordance with Aufbau principle?

(D) $n=4, \ell=0, m=0, s=+\frac{1}{2}$

(A) $n=3, \ell=2, m=+2, s=+\frac{1}{2}$

(B) $n=3, \ell=2, m=-2, s=+\frac{1}{2}$

(C) $n=4, \ell=1, m=0, s=+\frac{1}{2}$

JEE Main · 2026 · 04 Apr 2026 · Shift 1 · Atomic Structure

Which of the following is correct set of 4 quantum number of

1 9^{th}

electron in Chromium (Atomic number

= 24

) in accordance with Aufbau principle?

Answer: (D)

Filling orbitals in order of increasing energy, the first eighteen electrons of chromium complete

1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6}

. The nineteenth electron enters the

4 s

subshell. For a

4 s

electron the quantum numbers are

n = 4

ℓ = 0

m = 0

and

s = + \frac{1}{2}

JEE Main · 2026 · 04 Apr 2026 · Shift 1 · Single correct option