## Chemistry: The Central Science (13th Edition)

There are 2 possible values of $m_s$ for this orbital: $[+\frac{1}{2},-\frac{1}{2}]$.
The spin quantum number $m_s$ refers to the orientation of the spin axis of an electron. An electron can only spin in 2 directions and these directions are opposite from each other. $m_s$ can only have 2 possible values no matter which orbital being mentioned, which are $+\frac{1}{2}$ and $-\frac{1}{2}$.