-
442 BCE
Democritus
He named the atom, atom because it means uncut in Greek. He also thought that atoms shape was the same shape as what it made up -
John Dalton
All matter was made up of atoms.
All atoms of an element have a fixed mass.
Compounds contain atoms from different elements.
In compounds atoms from different elements always combine in a specific way. -
Marie Curie
She discovered radium and polonium. -
J.J. Thompson
He discovered the electron. -
E. Goldstein
He said that atoms must have both positive and negatively charged particles. He also said that the positively charged particles we called protons. -
Robert Millikan
He discovered that electrons have a negative charge. -
Ernest Rutherford
He discovered the nucleus of the atom and proved that the atom is mostly empty using his gold foil experiment. -
Niels Bohr
He created the modern atomic model that we use today in school because it is easy to understand. The protons and neutrons are in the center and the electrons go around the outside in shells or paths. -
Quantum Mechanical Model
Electrons don't move in paths around the atom they move around in waves. It would be impossible to actually see the electron. -
James Chadwick
He discovered neutrons and he said that they could be found in the nucleus of the atom.
