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310
Democritus
N.B. Date is ca 410 BCE
Democritus stated first that all matter was made up of atoms.
He thought that atoms were invisible and lasted forever, so they couldn't be divided further. -
350
Aristotle
N.B. Real Date is ca. 350 BCE
Aritotle belonged to the atomist school of thought. According to him, atoms are indestructible and inalterable and there are an infinite variety of shapes and sizes. They move through space and sometimes connect to form clusters, forming macroscopic items in world. -
Antoine Lavoisier
Lavoisier studied Air and Water which at the time were thought to be elements. He determin ed water was amde up of hydrogen and oxygen and that air was a mixture of mostly nitrogen and oxygen. He aslo divised chemical nomencalture that is still used today, with names like sulfates and sulfuric acid. Also, Lavoisier created the first chemistry textbook, which clearly stated the Law of Conversation of Mass. -
John Dalton
Dalton's main points on atomic theory were:
1. Elements are made up of extremely small particles known as atoms
2.Atoms of an element are identiacl in size, mass, and other properties, now not true due to isotopes.
3. Atoms can't be created, divided, or destroyed.
4. Atoms of different elements combine to form compounds in a simple whole number ratio.
5. In chemical reactions, atoms are combined, seperated, or rearranged. -
Henri Becquerel
Henri Bercquerel discovered radiation by accident when experimenting with uranium salts. -
Marie & Pierre Curie
The Curies discovered the elements of radiuma nd polonium when they were experimenting with radioactive materials. Marie Curie won 2 Nobel Prizes in different fields of science, the only person to do so. -
J. J. Thomson
J.J. Thomson discovered the electron and isotope. He also invented the "Plum Pudding" atom model. Thomson utilized a cathode tube in his experiments to dicover electrons by detecting an electric current. He was the teacher of Ernest Rutherford. It enhances the previous Dalton model by adding electrons and charged matter. -
Max Planck
Max Planck was the originator of the quantum theory. Planck theorized that energy was not continuosly released but released in quanta, or packets of energy. The quantum theory related to electrons as different quanta of energy meant that the elctron would be orbiting on a different power level. -
Robert Millikan
Robert Millikan is most known for the fact that he found the charge of an electron. He also won the Nobel Prize in Physics. -
Ernest Rutherford
Rutherford used a piece of gold foil and shot alpha particels at it. The expected result was for the particles to pass through because it was thought there was nothing dense enough to stop the particles. However, some alpha particles rebounded, showing that there was indeed something dense enought to stop the particles. Thus, the nucleus was dicovered. The proton was also discovered because the nucleus contrained a posuitie charge. The new Rutherford model uses a nucleus. Rutherford taught Bohr. -
Niels Bohr
Bohr stated that electrons move in orbits around the nucleus at diffferent energy levels. This lead to the development of Bohr's atom model. Bohr's model contained rings to show energy levels and orbitals of electrons around nucleus.
Bohr was the student of Rutherford and influenced other scientists. -
Henry Mosely
Mosely created the Atomic Number. Used to classify elements, this breakthrough helped to classify elements further. Mosely also influenced the endeavours of Ernest Rutherford. -
Erwin Shrodinger
Shrodinger introduced the Shrodinger Equation, a wav equation that describes the probability waves that govern the motion of small particles and how these waves are altered by external influences. He also experimented with radioactive materials and devised the Shrodinger cat equation. -
James Chadwick
James Chadwick discovered the Neutron. Chadwick discovered this unknown particle in the nucleus. Due to the fact that it had no charge it was known as the Neutron. Chadwick won a Noble Prize for this. He was also the student of Ernest Rutherford. -
Werner Heisenberg
Werner Hesienberg was one of the many scientists enlisted to create an atomic bomb. He won a Nobel prize for his creation of Quantum Mechanics. He was the student of Niels Bohr. Heisenberg is also known well for his Uncertainty principle. It states that you can't know both the velocity and the momentum of a particle simultaneously, basically you can't know the location of an electron.
