Both
and
can be calculated in the Bohr theory from Planck's constant and
the charge and mass of the electron, and checked against experimental
values.

The most important new idea in Bohr's model of the atom is the conclusion
that not every energy is possible for the atom.

The energy of an atom is restricted, or quantized.

This quantization of energy arises from Assumption 2 (standing waves
around the circumference of the orbit) just as the overtones that
one can get from a vibrating violin string are determined by its
length (standing waves along the string).