who developed the first theories of nuclear physics?

Answer 1

Not quite. Dalton only went as far as hypothesizing the existence of atoms, which he thought where unit objects. The first theories of nuclear physics came about when the electron was determined to be a separable part of an atom, leading to the question of what remain from that. A number of scientists in the early 20th century pieced together our current theories of the nucleus, such as the discovery of protons, neutrons, and the binding energies contained that lead to atomic energy.

Answer 2

John Dalton in 1803.