Atomic Timeline
Democritus-440 BCE
Atoms are small, hard particles
Atoms are "uncuttable"
Atoms are made of a single material formed into different shapes and sizes
Bohr-1913
Dalton-1803
Atoms of the same elements are exactly alike and atoms of different elements are different.
He conducted experiments in combing elements
All substances are made of atoms
Thomson-1897
There are small, negatively charged particles (electrons) inside an atom
He conducted the cathode-ray tube experiment
His theory of atomic structure led to the "plum-pudding" model.
Rutherford-1909-1911
Most of an atom's mass is in the nucleus. It is small, dense, and positively charged
He conducted the gold foil experiment
Atoms contain mostly empty space
Electrons travel in specific paths, or energy levels
Schrodinger and Heisenberg-1926 & 1927
Electrons are found in electron clouds, not paths
His theory stated that is is impossible to simultaneously determine the velocity and location of an electron
