Question

What is the physical significance of principal quantum number?

Answer 1

In quantum mechanics, the principal quantum number (symbolized n) is one of four quantum numbers which are assigned to all electrons in an atom to describe that electron's state. As a discrete variable, the principal quantum number is always an integer. As n increases, the number of electronic shells increases and the electron spends more time farther from the nucleus. As n increases, the electron is also at a higher energy and is, therefore, less tightly bound to the nucleus. The total energy of an electron, as described below, is a negative inverse quadratic function of the principal quantum number n.