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400
Democritus (400 BC)
First proposed the idea that matter was made out of tiny, indivisible particles called atoms. -
Period: 400 to
History of Atomic Structure
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Robert Boyle
Came up with the well known law “Boyle’s Law”, volume of a gas varies inversely with pressure -
Antoine Lavoisier
Determined the Law of Conservation of Matter by extensive experimentation. -
John Dalton
- All matter is made of particles called atoms. 2.Atoms are indivisible. 3.Atoms can not be created or destroyed.
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Dmitri Mendeleev
Created the Periodic Law, created his own version of the periodic table of elements, and corrected the elements already discovered -
Eugen Goldstein
He was an early investigator of discharge tubes, the discoverer of anode rays, and is sometimes credited with the discovery of the proton. -
J.J Thomson
Concluded that since cathode rays were attracted to a positive plate, they consisted of negatively charged particles. Plum pudding model. -
Robert Millikan
Set up “oil drop experiment” that determined the size of the charge of the electron. -
Ernest Rutherford
Discovered the nucleus. He concluded that particles were deflected at large angles or same path. There is a small. dense core of our positively charged nucleus. -
Niels Bohr
1.Electrons move around the nucleus in fixed paths called orbits.
2.Electrons in an orbit have a fixed amount of energy.
3.As long as an electron stays in one energy level. It doesn’t gain or lose electrons.
4. When an atom absorbs energy, electrons jump from lower energy levels to higher ones, but don’t remain there long due to instability.
5. If energy is lost, electrons fall to a lower level and light is given out. -
Henry Moseley
developed the application of X-ray spectra to study atomic structure -
Max Planck
originated quantum theory, explains the nature and behavior of matter and energy on the atomic and subatomic level. -
Erwin Schroedinger
combined the equations for the behavior of waves with the de Broglie equation to generate a mathematical model for the distribution of electrons in an atom. Electron cloud model -
James Chadwick
Discovered the neutron by bombarding beryllium with alpha particles. particles with no charge came from beryllium.
