Written by the Fiveable Content Team โข Last updated September 2025
Written by the Fiveable Content Team โข Last updated September 2025
Definition
The magnetic quantum number, denoted as $m_s$, describes the spin orientation of an electron within an orbital. It can take one of two possible values: $+\frac{1}{2}$ or $-\frac{1}{2}$.
5 Must Know Facts For Your Next Test
$m_s$ indicates the direction of the electron's intrinsic spin.
The possible values for $m_s$ are always $+\frac{1}{2}$ and $-\frac{1}{2}$.
An electron with $m_s = +\frac{1}{2}$ is said to have 'spin up,' while one with $m_s = -\frac{1}{2}$ has 'spin down.'
$m_s$ is crucial for determining the electron configuration and behavior in a magnetic field.
Pauli Exclusion Principle states that no two electrons in the same atom can have identical sets of quantum numbers, including $m_s$.
Review Questions
Related terms
$n$ (Principal Quantum Number): Defines the main energy level occupied by an electron in an atom and determines its relative distance from the nucleus.
$l$ (Azimuthal Quantum Number): Describes the shape of the orbital and subshell where an electron is located, ranging from 0 to $(n-1)$.
$m_l$ (Magnetic Quantum Number): Specifies the orientation of an orbital within a subshell, taking on integer values between $-l$ and $l$, inclusive.