principal quantum number

This term is a technical designation used exclusively within the field of quantum chemistry and atomic physics. It refers to the primary energy shell of an atom, where a higher value indicates that the electron is further from the nucleus and possesses higher energy.

In a pedagogical context, it is often denoted by the symbol n. Because it represents a discrete energy level, it is always expressed as a positive integer (1, 2, 3, etc.), and cannot be a fraction or a negative number.