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600 BCE
Dharmakirti
Primary theorist in Buddhist Atomism, which states that all matter is made up of tiny atoms that are momentary flashes of energy. -
500 BCE
Leucippus and Democritus
Came up with the idea of Atomism, which states that all matter is made of small particles called atoms that are indivisible. They came up with this idea around 500BC. -
Alchemists
Corpuscularianism is similar to Atomism, except atoms are divisible and can combine. Important principles include: Same elements can be combined at different ratios to produce different compounds, and that molecules can have secondary properties. This theory was used by scientists such as Newton and Boyle in alchemy. -
John Dalton
Main points of the Dalton theory:
1. Elements are made of small particles
2. Atoms of a given element is identical in properties
3. Atoms cannot be created or destroyed
4. Atoms can be combined in whole number ratios to make compounds
5. Atoms in chemical reactions are combined, separated, or rearranged. -
Sir Joseph John Thomson
Discovered the electron through cathode ray experiments. Proved that there are subatomic particles smaller than atoms. He also evidence of isotopes in 1912. -
Max Planck
Planck postulated in 1900 that all electromagnetic energy emitted from black body radiation must be a multiple of Planck's constant. This was a solution to the Ultraviolet catastrophe. -
Marie Curie
Shared the Nobel prize of physics in 1903 for the research into radiation. She hypothesized that radiation came from atoms themselves, instead of from interactions between molecules. -
Plum Pudding model
Suggested by SIr Joseph John Thomson, which stated that atoms are negatively charged electrons occupying a positively charged space. -
Hantaro Nagaoka
Hantaro Nagaoka was a physics professor in Japan. He rejected the Plum Pudding model, instead creating something called the Saturnian model. Where there is a positively charged centre, surrounded by electrons orbiting around it similar to Saturn's rings, held by electrostatic forces.(Wow this theory sounds really familiar) -
Albert Einstein
Explained the photoelectric effect, laying groundwork to the idea of wave-particle duality. He stated that light can be packed into discrete quanta of energy called photons, which revolutionized quantum physics. -
Geiger–Marsden experiment
Hans Geiger and Ernest Mardsen shot alpha particles at a sheet of gold foil. Instead of going straight through according to the Plum Pudding model, many alpha particles were reflected or scattered. -
The Rutherford Model
Ernest Rutherford disproved the earlier Plum Pudding model. Stating that atoms have a strong positively charged core, surrounded by negatively charged electrons in different orbits. he proved this from the results of the famous gold foil experiment. -
Rutherford–Bohr model
The Rutherford-Bohr model, is an improved version of the older Rutherford model. Which states that the core of the atom is a positively charged nucleus, which is surrounded by electrons in a similar fashion to the solar system. -
Louis Victor Pierre Raymond de Broglie
Louis de Broglie postulated in 1924, that all matter has wave properties and stated that electrons can also act like waves in addition to being particles. -
Pauli Exclusion Principle
Pauli exclusion principle states that two or more identical electrons with the same spin cannot occupy the same quantum state. Formulated in 1925 by Wolfgang Pauli. -
Erwin Schrödinger
Erwin Schrödinger came up with the Schrödinger Equation, which can be used to describe the wave function of a quantum-mechanical system. This is important since electrons are both waves and particles according to the quantum theory. -
Heisenberg's Uncertainty Principle
Heisenberg's Uncertainty Principle states that the momentum and position of a particle cannot be accurate determined. If you know the exact position you the momentum is uncertain, if you know the exact momentum the position is uncertain. This is important because at this time is where the quantum model started to appear. Which states that particles are also waves. -
James Chadwick
Discovered the neutron, he also helped with the American Manhattan project. -
Lise Meitner
Led a team and discovered nuclear fission. -
Ronald Gillespie
Worked extensively on the VSPER model. Along with helping develop the LCP theory, which describes how repulsion affects the geometry of bonding.
