It became clear that a fairly radical departure from
the established principles of classical mechanics and electromagnetism
would be needed to understand the structure of atoms and the relation
of atomic structure to atomic spectra Bohr combined classical and early
quantum concepts and gave his theory in the form of three postulates These are :
(i)
Bohr’s first postulate was that an electron in an atom could revolve
in certain stable orbits without the emission of radiant energy,
contrary to the predictions of electromagnetic theory According to
this postulate, each atom has certain definite stable states in which it
Rationalised 2023-24
299
Atoms
can exist, and each possible state has definite total energy