What was different about the atomic theory proposed by niels bohr?

the atom's mass was limited to the center of the atom
the addition of electrons to orbit the nucleus
electrons energy levels related to their orbits
a positively charged nucleus in the center of the atom

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.

0.88m hope i am correct : )