The angular momentum quantum number $\ell$ can take values from $0$ to $n-1$, so for $n = 2$, $\ell$ can be $0$ or $1$. The magnetic quantum number $m_{\ell}$ can take values from $-\ell$ to $\ell$, so for $\ell = 0$, $m_{\ell}$ can only be $0$, and for $\ell =
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