Question
Which of the following is correct set of 4 quantum numbers of 19^ th electron in Chromium (Atomic number = 24) in accordance with Aufbau principle?
JEE Main
Chemistry
Structure of Atom
2026
JEE Main 2026 (04 April Shift 1)
JEE Main Chemistry Question (2026) — Solution
Options
- A. n = 3, l = 2, m = +2, s = + 1 2
- B. n = 3, l = 2, m = -2, s = + 1 2
- C. n = 4, l = 1, m = 0, s = + 1 2
- D. n = 4, l = 0, m = 0, s = + 1 2
Answer
D. n = 4, l = 0, m = 0, s = + 1 2
Step-by-step solution
The atomic number of Chromium is 24. According to the Aufbau principle, the order of filling of electrons is 1s, 2s, 2p, 3s, 3p, 4s, 3d. The electronic configuration of the first 18 electrons is 1s^2 2s^2 2p^6 3s^2 3p^6. The 19^ th electron enters the 4s orbital. For the 4s orbital, the quantum numbers are: Principal quantum number, n = 4 Azimuthal quantum number, l = 0 Magnetic quantum number, m = 0 Spin quantum number, s = + 1 2 or - 1 2 This matches the set given in the fourth option. Answer: n = 4, l = 0, m = 0, s = + 1 2
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