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Period: 460 BCE to 1900 BCE
Atomic theory evolution
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4 BCE
Democritus
If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Democritus thought that it ended at some point, a smallest possible bit of matter. https://www.conejousd.org/Portals/49/Departments/Science/ponce/AP%20Chem/Handouts/Short%20History%20of%20Atoms.pdf. -
Dalton
1800’s. “Studying the beam in a cathode ray tube. The beam could be bent by a magnet or an electric charge which showed that the beam had a negative charge.” He found out compounds could be made of atoms but in different amounts. https://www.conejousd.org/Portals/49/Departments/Science/ponce/AP%20Chem/Handouts/Short%20History%20of%20Atoms.pdf -
Thomson
“ He discovered the electron and proposed a model for the structure of the atom.” “ His model looked like raisins stuck on the surface of a lump of pudding.” https://www.conejousd.org/Portals/49/Departments/Science/ponce/AP%20Chem/Handouts/Short%20History%20of%20Atoms.pdf -
Rutherford
Experimented by bombarding atoms with alpha rays.” Most of the alpha particles went smoothly through the foil. Surprisingly, an occasional alpha bent sharply from its original path,.” He discovered that there must be electrons in the empty space. -
Bohr
"Here are some rules that seem impossible, but they describe the way atoms operate, so let's pretend they're correct and use them." 1. Electrons can orbit only at certain allowed distances from the nucleus. #2. Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. -
Rutherford discovered Nuclei
Rutherford discovered the particles of the nucleus is positive charges of matter.
