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JEE Main20264 April 2026Morning ShiftChemistryStructure of AtomActual

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?

Options

  1. An = 3, l = 2, m = +2, s = + 1 2
  2. Bn = 3, l = 2, m = -2, s = + 1 2
  3. Cn = 4, l = 1, m = 0, s = + 1 2
  4. Dn = 4, l = 0, m = 0, s = + 1 2

Correct 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

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