Question

______ discovered electronic shells​

Answer 1

Bohr. In 1913 Bohr proposed his quantized shell model of the atom (see Bohr atomic model) to explain how electrons can have stable orbits around the nucleus

Answer 2

Answer:

In 1913, Niels Bohr proposed a theory for the hydrogen atom, based on quantum theory that some physical quantities only take discrete values. ... Bohr's model explained why atoms only emit light of fixed wavelengths, and later incorporated the theories on light quanta. He also had founded elctronic shells.