Ιf light or the photon is considered as both particle and wave could the same apply to the electron? If a water wave is water spread in space, could the electron be considered as charge/energy "smudged" in space? The Schrödinger equation and the wave function Ψ provide a model for the related probabilities. The quantum numbers are the solution of the equation. They are related to the rotational motion from classical mechanics! Is this why we say "quantum mechanics"?

Explain the "sodium doublet", the two spectral lines of sodium, due to the internal magnetic field of the sodium atom, resulting from the orbital angular momentum and the spin.

Determine the magnetic field of the Sun using the Zeeman effect on sodium. Spectral lines due to the "spin-orbit interaction" (linked to the internal magnetic field of the atom) are split further under the effect of an external magnetic field.