Can L Be Negative In Quantum Numbers. However, the magnetic quantum number, $m_l$, can be negative. The magnetic quantum number, m ℓ, specifies the spatial orientation of a particular orbital.
When ℓ = 3, the allowed m ℓ values are −3, −2, −1, 0, +1, +2, +3. While it is not possible to have negative values for some quantum numbers, such as the principal quantum number, there are others, such as the magnetic quantum. For example, for an s orbital, ℓ = 0, and the only value of m ℓ is 0;