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465 BCE
Democritus
Findings:
-Believed all matter was composed of atoms.
- Believed each atom was separated by a distinctive amount of space
-He believed atoms were solid and different shapes.
*He's one of the greatest Promoter of the atomic theory of his time, but his Beliefs and theories were refused and ignored for many centuries. -
John Dalton
Findings:
-He believed that elements are made of atoms.
-His description of atoms were blank but he was aware of it having structure.
- Believed that the atoms of an element are equal in their masses.
- Believed that atoms of different elements have different masses.
-Dalton proposed that the combination of atoms could be measured in simplistic, whole number ratios.
*John Dalton was extremely important to atomic history. He was the first to propose an actual "atomic theory." -
J.J. Thomson
Findings:
-Proposed that cathode rays were made up of smaller particles than atoms which led to the suggestion that those particles made up the matter inside of an atom.
-Discovered electrons.
*Thomson made a shocking claim that led to finding out about the electron. -
Robert Millikan
Findings:
-Conducted an experiment known as the oil-drop Experiment.
In this experiment he observed the electric fields on drops of oil. He used oil instead of water because of evaporation.
-The results of the experiment allowed him to conclude the charge and mass of the electron.
*Millikan accurately discovered information about the electron, such as charge and mass, using an expirement he conducted himself. -
Ernest Rutherford
Findings:
-Discovered the proton
-Used the "Gold Foil Expirement" to reach his discoveries.
**The Gold Foil Experiment: Rutherford shot alpha particles (positively charged particles) at an extremely thin sheet of gold. He did this to see whether the particles would pass through or deflect off. During the test he saw that many of the particles were deflecting at an angle, which led to the conclusion that an atoms mass was concentrated in the center, which led to the discovery of the nucleus. -
Neils Bohr
Findings:
-Bohr elaborated on Rutherford's theory of there being negatively charged electrons around the atom.
-Discovered the "Valance Shell" and proposed that it held electrons which determined many of the properties of the atom.
-He also discovered and studied how atoms emit radiation.
* Overall, Neils Bohr made many discoveries on atomic structure, focusing on electrons and valence shells. -
Werner Heisenberg
Findings:
-Led the foundation of quantum physics.
-Advanced the quantum theory.
-"Uncertainty Principle" which basically stated that it is impossible to know a particles position and velocity.
*Led a breakthrough in Quantum physics and refined a measure of controversy on the atom. -
Erwin Schrodinger
Findings:
-Studied Quantum Physics.
-Published work of the idea that wave mechanics was the actual mathematical model of the atom.
- Erwins work greatly influenced other scientists.
*All in all, Schrodinger was known for his work on Wave Mechanics and attempted to explain the movement of electrons as a wave in the atom. -
James Chadwick
Findings:
-Discovered the Neutron.
-Found out that the nucleus could raise the atomic mass of an atom without actually containing a electrical charge.
-Established that atomic number is influenced by the number of protons the atom contains.
*Advanced the knowledge of the atoms structure, and discovered the neutron. -
Enrico Fermi
-Studied atomic theory.
-Experimented with atomic chain reactions.
-Was able to figure out the atomic chain reaction in order for an atomic bomb to be built.
*Assisted with the first atomic bomb being built and had great success in chain reactions.
