💏intro to chemistry review

Quantum numbers

Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025

Definition

Quantum numbers are a set of numerical values that describe the unique quantum state of an electron in an atom. They provide information about the electron's energy, orbital shape, orbital orientation, and spin.

AP course connection

Topic 6.1: 6.1 Electromagnetic Energy

Unit 6

5 Must Know Facts For Your Next Test

  1. The four types of quantum numbers are the principal quantum number ($n$), angular momentum quantum number ($l$), magnetic quantum number ($m_l$), and spin quantum number ($m_s$).
  2. The principal quantum number ($n$) indicates the energy level and size of the orbital and can be any positive integer.
  3. The angular momentum quantum number ($l$) determines the shape of the orbital and can have values from 0 to $n-1$.
  4. The magnetic quantum number ($m_l$) specifies the orientation of the orbital in space and can range from $-l$ to $+l$.
  5. The spin quantum number ($m_s$) describes the direction of the electron's spin and can either be $+\frac{1}{2}$ or $-\frac{1}{2}$.
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