Page "Aage Bohr" Paragraph 6

By the late 1940s it was known that the properties of atomic nucleus could not be explained by the then-current models ( such as the liquid drop model developed by Niels Bohr amongst others ).

The shell model, developed in 1949, allowed some additional features to be explained, in particular the so-called magic numbers.

However, there were also properties which could not be explained, including the non-spherical distribution of charge in certain nuclei.