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

For hydrogen, for a given value of $n$, the energies of the $s, p, d, f$ subshells are the same.
For hydrogen, for a given value of $n$, the energies of all subshells are the same, due to the fact that there is only one electron in the atom. (That means for example, for the third shell of hydrogen ($n=3$), the energies of all subshells $3s, 3p, 3d$ are the same) Therefore, for hydrogen, for a given value of $n$, the energies of the $s, p, d, f$ subshells are the same.