The Principal quantum number (symbolized ‘n’) is one of the four quantum numbers assigned to each electron in an atom to describe the electron’s state.
Principal quantum number is used to describe the energy of an electron.
Atomic shells denoted by the capital letters K (for n = 1), L (for n = 2), M (for n = 3), N (for n = 4),… .
Reference Source:
[1] Wikipedia Contributors. Principal quantum number. Wikipedia. Published November 17, 2021. Accessed January 14, 2022. https://en.wikipedia.org/wiki/Principal_quantum_number.
[2] Hydrogen Schrodinger Equation. Gsu.edu. Published 2022. Accessed January 14, 2022. http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/hydrad.html#c3.
[3] Principal quantum number – Knowino. Theochem.ru.nl. Published 2022. Accessed January 14, 2022.https://www.theochem.ru.nl/~pwormer/Knowino/knowino.org/wiki/Principal_quantum_number.html.