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400
BCE Democritus
Life: 460BCE-370BCE
Discovery made: around 400BCE He had a philosophy that everything was made of atoms, which was the smallest unit of matter. He was the first to think of the atomic universe. He is the father of modern science. He proved his theories with math. -
Dalton
Life: 1766-1844
Discovery made: 1803 He created the modern atomic theory. He also created the billard ball model. He begun developing his theory when he noted that carbon and oxygen combined to form proportional compounds. -
Billiard Ball Model
Dalton created the billiard ball model. He thought that the atom was a solid, indivisible sphere. The model was just a sphere. -
Cathode Ray Tube Experiment
JJ Thomson conducted the cathode ray tube experiment, which helped discover the electron. The cathode ray tube demonstrated that cathode rays could be deflected by a magnetic field, and that their negative charge was not a separate phenomenon. It also proved that the deflection of the rays were the same. It would accelerate and deflect electron beams onto the screen to create images. -
JJ Thomson
Life: 1856-1940
Discovery made: 1897 Thomson was an English physicist that discovered the electron. He showed that cathode rays were composed of a previously unknown negatively charged particle. The electron was also the first subatomic particle discovered. He is also credited with finding the first evidence of isotopes. He also invented the mass spectrometer. -
Electron Discovery
The electron was discovered by JJ Thomson when he was experimenting with cathode rays. Thomson measured the ratio of the mass of the cathode ray to its electrical charge. -
Plum Pudding Model
The plum pudding model was created by JJ Thomson. The model was created to incorporate the newly discovered electron. It was a circle that represented a spherical cloud of positive energy with electron inside it. However this model was abandoned because it lacked the atomic nucleus. -
Gold Foil Experiment
The gold foil experiment was ran by Ernest Rutherford. The experiments discovered that every atom contains a nucleus where its positive charge contains most of its mass. Rutherford deduced this by observing how alpha particles are scattered when they strike a thin metal foil. -
Rutherford
Life: 1871-1937
Discovery made: 1909 He is considered the father of nuclear physics. He also discovered the proton and the atomic nucleus. He also produced his own theory entitled "Theory of Atomic Disintegration. His most famous work however is the "gold foil experiment". He also created the nuclear model. -
Bohr
Life: 1885-1962
Discovery made: around 1911 He was a Danish physicist who made foundational contributions to understanding the structure of an atom and quantum theory. He also developed the Bohr model. He proposed that the electrons revolve in stable orbits around the atomic nucleus but can jump from energy level to another. -
Nuclear Model
Rutherford invented this model. It showed the newly discovered atomic nucleus. In the middle there was the mass of molecules that were protons and mass while electrons orbited the nucleus. It had rings going in different directions to show random movement. -
Bohr Model
Bohr created the bohr model. It proposed his quantized shell model of the atom to explain how electrons can have a stable orbits around the nucleus. It was similar to the nuclear model except it had circles around the nucleus that showed fixed movement. -
Proton Discovery
Ernest Rutherford discovered through multiple experiments that explored radioactivity. In doing one experiment he discovered that the atom must have a concentrated positive center that contains most of the atoms mass. -
Schrodinger and Heisenberg
Discovery made: mid 1920s The two of them are credited with significantly reformulating Quantum theory and mechanics. Heisenberg was a key scientist in the Uranium Club, a german nuclear energy project. Schrodinger also formulated the wave equation for wave mechanics created the quantum mechanical model. -
Quantum Mechanical Model
Schrodinger was the scientist who invented the quantum mechanical model. The model is based on quantum theory. It uses complex shapes called orbitals (or electron clouds), which are volumes of space that show where an electron is likely to be. The orbitals still surrounded the nucleus. The more dense or darker an area of the model, the greater chance an electron would be there. This is the first model to introduce the concept of sub-energy levels. -
Neutron Discovery
James Chadwick discovered the neutron when he used scattering data to calculate the mass of the neutral particle. He also used DeBrolie wavelength.
