| A | B |
|---|
| Aristotle | ancient Greek philosopher who believed that matter could always be divided into smaller parts and there were no such things as atoms |
| Democritus | ancient Greek philosopher who believed that matter existed as indivisible units he called atoms |
| John Dalton | discovered the Law of Multiple Proportions that became the basis for the modern atomic concept and the way we write compound formulae |
| William Crookes | inventor of the "cathode ray tube" which produced a strange king of light |
| J.J. Thomson | discovered the first known subatomic particle, the electron, developed the "plum pudding" model of the atom |
| Ernest Rutherford | discovered the atomic nucleus, discovered the proton, developed the planetary atomic model |
| James Chadwick | discovered the neutron, led the British effort to make an atomic bomb in WW II |
| Henry Moseley | used x-ray diffraction techniques to determine the number of protons in the atomic nucleus |
| Niels Bohr | explained the emission spectra of hydrogen |
| Louis De Broglie | explained electrons are both particles and wave energy |
| Erwin Schroedinger | expanded Bohr's quantum mechanics to all electrons of all elements |
| Werner Heisenberg | the "Uncertainty Principle", it is not possible to determine the electron's velocity, mass, and position simultaneously. led German effort to build atomic bomb in WW II |
