Question

How did max planck contribute to the modern atomic theory?

Answer 1

Max Planck for the first time introduced the notion of light quantum (quantum nature of electromagnetic radiation) to explain the blackbody curve. Einstein extended the idea to explain photoelectric effect.
Neils Bohr, the danish physics giant introduced quantized non radiating energy levels in an atom in contradiction to Maxwell's EM theory and incorporated Planck's concept of photons to explain the existence of discrete lines in the atomic spectra.
The Frank - Hertz experiment verified the concept of quantum energy levels and quantized nature of EM radiation was confirmed by Millikan.
This was the beginning of the quantum age and the important results of quantum physics started pouring in thereafter.