John Dalton pictures atoms as tiny, indestructible particles, with no internal structure.
J.J. Thomson, a British scientist, discovers the electron. This later leads to his "plum-pudding" model. He pictures electrons embedded in a sphere of positive electrical charges
Hantaro Nagaoka, a Japanese physicist, suggests that an atom has a central nucleus. Electrons move in orbits like the rings around Saturn.
In Niels Bohr's model, the electron moves in a circular orbit at fixed distances from the nucleus
French physicist Louis de Broglie proposes that moving particles like electrons have some properties of waves. Within a few years, experimental evidence supports the idea
Erwin Schrodinger develops the mathematical equations to describe the motion of electrons in the atom. His work leads to the electron cloud model.
James Chadwick, an English physicist, confirms the existence of neutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons.