Principal quantum number

Definition

The principal quantum number, denoted as $n$, indicates the main energy level or shell occupied by an electron in an atom. It is a positive integer that determines the size and energy of the orbital.

5 Must Know Facts For Your Next Test

1. The principal quantum number $n$ can take any positive integer value (1, 2, 3,...).
2. As $n$ increases, the electron's average distance from the nucleus also increases, meaning higher energy levels are farther from the nucleus.
3. The maximum number of electrons that can occupy a given energy level is given by $2n^2$.
4. Each principal quantum number corresponds to a specific shell: K (for $n=1$), L (for $n=2$), M (for $n=3$), etc.
5. Higher principal quantum numbers indicate orbitals with larger sizes and higher energies.

Review Questions

• What does the principal quantum number $n$ signify in terms of electron configuration?
• How is the maximum number of electrons in an energy level determined using $n$?
• What happens to the size and energy of an orbital as the principal quantum number increases?

Related terms

Angular Momentum Quantum Number: Denoted as $l$, it determines the shape of an electron's orbital within a given shell.

Magnetic Quantum Number: $m_l$, specifies the orientation of an orbital around the nucleus within a subshell.

Spin Quantum Number: $m_s$, represents one of two possible orientations of an electron's spin: +1/2 or -1/2.