Hydrogen has been a great laboratory for Quantum Mechanics.
After Hydrogen, Helium is the simplest atom we can use to begin to
study atomic physics.
Helium has two protons in the nucleus (
), usually two neutrons (
),
and two electrons bound to the nucleus.
This material is covered in
Gasiorowicz Chapters 18,
in
Cohen-Tannoudji et al. Complement
,
and briefly in Griffiths Chapter 7.