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John Dalton pictures atoms as tiny, indestructible particles, with no internal structure.
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J. J. Thompson, a British scientist, discovers the electron.
This later leads to his "plum-pudding" model. He pictures electrons embedded in a sphere of positive electrical charge. -
Hantaro Nagaoka, a Japanese physicist, suggests that an atom has a central nucleus.
Electrons move in orbits like the rings around Saturn. -
New Zealand physicist Ernest Rutherford finds that an atom has a small, dense, positively charged nucleus.
Electrons move around the nucleus. -
In Niels Bohr's model, the electron moves in a circular orbit at fixed distances from the nucleus.
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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 mathematical equations to describe the motion of electrons in atoms.
His work leads to the electron cloud model. The quantum mechanical model comes from the mathematical solutions to the Schrodinger equation. -
James Chadwick, and English physicist, confirms the existence of neutrons, which have no charge.
Atomic nuclei contain neutrons and positively charged protons.