Different shapes, one energy

For hydrogen in this nonrelativistic model, Eₙ = −1/(2n²) Hartree. Changing l or m changes the cloud but does not change its energy at fixed n. This degeneracy is specific to the Coulomb model: it does not describe multi-electron atoms, fine structure or external fields. The ladder uses one common energy scale and marks zero as the ionization limit. Higher n levels become closer together.