Niels Bohr (1885-1962), a Danish physicist, earned his Ph.D. in physics in 1911, and his university studies involved electrons.
Coincidently, the electron was the new 'hot' area of physics study, so as soon as Bohr finished his university studies, he went to England to study with J.J. Thomson, who had received a Nobel Prize in Physics in 1906 for his discovery of the electron.
Not to be dissuaded, Bohr went to visit a former student of Thomson's, Ernest Rutherford. Using the results of his gold foil experiments, in 1911 Rutherford theorized that the atom had a dense, central nucleus with positive charges, and it had orbiting electrons carrying negative charges.
Bohr wasn't completely comfortable with Rutherford's model of the atom. For one thing, the rules of classical physics dictated that Rutherford's atomic model would be very unstable. The orbiting electrons would have to give off energy and would eventually spiral down into the nucleus, making the atom collapse (in what would probably be a really big explosion!).