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460 BCE
Democritus
Atoms are "uncuttable"
Atoms are small, hard particles
Atoms constantly move -
460 BCE
Democritus
Atoms are homogeneous meaning they have no internal structure. He stated atoms was solid, and stated all atoms differ in size, shape, mass, position and arrangement, with a void exists between them. -
Dalton
All substances are made of atoms
Atoms of different elements are different
Atoms of the same element are exactly alike
Elements combine in specific proportions
He conducted experiments in combining elements -
Dalton
All matter is composed of very small things -
Thomson
He conducted the cathode-ray tube experiment.
His theory of the atomic structure lead to the "plum pudding" model.
There are small, negatively charged particles inside an atom. -
Thomson
The atom was a sphere embedded with electrons. The sphere had positive positive charges throughout it and negatively charged particles were also scattered across this model. -
Rutherford
Atoms contain mostly empty space
Electrons move in empty space in the atom
He conducted the gold foil experiment
Most of an atom's mass is in the nucleus -
Rutherford
The electrons were embedded in a positively charged atom like plums in a pudding. -
Bohr
Electrons jump between levels from path to path
Electrons travel in definite paths -
Bohr
The electrons could only orbit the nucleus in certain special orbits at different energy levels around the nucleus. -
Schrodinger and Heisenberg
Electrons are found in electron clouds, not paths. - Both
Electron paths cannot be predicted. - Schrodinger -
Schrodinger and Heisenberg
The nucleus is in the middle
