Quantum numbers

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.

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 $-\frac{1}{2}$.

Review Questions

• What does each of the four quantum numbers represent?
• How do you determine the possible values for the angular momentum quantum number ($l$)?
• What is the significance of the magnetic quantum number ($m_l$) for an electron in an atom?

Related terms

Orbital:

A region in an atom where there is a high probability of finding electrons.

Electron Configuration:

The distribution of electrons among different orbitals in an atom.

Pauli Exclusion Principle:

A principle stating that no two electrons in an atom can have identical sets of all four quantum numbers.