Helium (He) — its atomic orbitalsHelium is element 2: period 1, group 18, noble gas of the s block. Its ground-state configuration is 1s², so its outermost occupied shell is n = 1 and holds 2 electrons.Each orbital below is the hydrogen-like solution at the effective nuclear charge Slater's rules give its subshell, so its angular nodes fall where the wavefunction changes sign rather than where a drawing puts them. Slater screening gives the effective charge; the energy is the hydrogen-like −13.606 Z_eff²/n², and ⟨r⟩ the mean radius of one orbital of the subshell.

Subshell

Electrons

Z_eff

Energy (eV)

Radial nodes

Angular nodes

⟨r⟩ (Å)

1.70

-39.32

0.467

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