In Chapter 5, you solved the Schrodinger equation for the hydrogen atom using spherical coordinates, finding the quantum numbers $n$, $l$, $m$. The energy depended only on $n$: $E_n = -13.6\,\text{eV}/n^2$. For a given $n$, all states with different $l$ and $m$ values had the same energy. This $n^2$