Quantum Numbers of Potassium Valence Electron | JEE Main PYQ | Structure of Atom
Q. The four quantum numbers for the electron in the outermost orbital of potassium (atomic number 19) are:
(A) n = 3, l = 0, m = 1, s = +1/2
(B) n = 4, l = 0, m = 0, s = +1/2
(C) n = 2, l = 0, m = 0, s = +1/2
(D) n = 4, l = 2, m = −1, s = +1/2

Correct Answer: (B)

Explanation

Electronic configuration of potassium (Z = 19):

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

The outermost electron lies in 4s orbital.

Therefore: n = 4, l = 0, m = 0, s = +1/2

Previous Year Questions – Structure of Atom
The ionization energy of sodium in kJ mol⁻¹, if electromagnetic radiation of wavelength 242 nm is just sufficient to ionize sodium atom is ______.
The correct set of four quantum numbers for the valence electron of rubidium atom (Z = 37) is:
Number of spectral lines obtained in He⁺ spectra, when an electron makes transition from fifth excited state to first excited state will be ______.
The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency A × 10¹² hertz and that has a radiant intensity in that direction of 1/B watt per steradian. A and B are respectively:
Based on Heisenberg's uncertainty principle, the uncertainty in the velocity of the electron to be found within an atomic nucleus of diameter 10⁻¹⁵ m is ______ × 10⁹ m s⁻¹.
JEE Main Full Study Material – Physics & Chemistry

Updated for JEE Main 2026: This PYQ is important for JEE Mains, JEE Advanced and other competitive exams. Practice more questions from this chapter.

Scroll to Top