Energy levels

Turning points in physics         Hodder        Collins

https://phet.colorado.edu/sims/html/molecules-and-light/latest/molecules-and-light_all.html

Characteristic X rays and Auger electrons 

Spectrum of Auger electrons 

Energy levels and spectra  

Planetary model of the atom - phet

Excitation by light - phet

Landscape of the micro world

What atoms are made of?         Nucleus - mass and charge       

Electrons       Ions          Specific charge

 Bohr Model                       

Ionization energy and ground state

Discharge tube and excitation by collisions        

De-excitation and emission spectra

 Absorption spectroscopy