For a completely stripped $\mathrm{He}^{+}$ ion (a single-electron species), the correct increasing

Question

For a completely stripped $\mathrm{He}^{+}$ ion (a single-electron species), the correct increasing order of energy for its various atomic orbitals is accurately represented by

Professor PC Thomas Classes · Answer

(d) : The $\mathrm{He}^{+}$ ion is a hydrogen-like, single-electron species. In any such species, the energy of an atomic orbital is determined exclusively by its principal quantum number ($n$), completely independent of its azimuthal quantum number ($l$). Therefore, all subshells belonging to the same principal shell are entirely degenerate. The correct energy sequence is $1s < 2s = 2p < 3s = 3p = 3d < 4s$.