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430 BCE
Basic Structure of Matter
Leucippus and Democritus argued that all matter was composed of small, finite particles that they called atomos -
340 BCE
Aristotle
came to the conclusion that matter consisted of various combinations of the four “elements”—fire, earth, air, and water—and could be infinitely divided. -
Dalton's Atomic Theory
hypotheses about the microscopic features of matter. -
Avogadro's Hypothesis
created hypothesis that equal volumes of different gases contain an equal number of molecules and realized that elements could exist in the form of molecules rather than as individual atoms. -
Thallium Discovered
Sir William Crookes discovered the element thallium, a negative charge in atom, and developed the Crookes tubes which is used for demonstrating cathode rays. -
JJ Tomson
discovered electron using cathode rays, plum pudding model -
Quantum Theory Founded
Planck founded of the Quantum Theory, the quantum theory focuses on the nature of atoms. The Theory explains how energy exists in individual units in the same way that matter does, not just waves. -
Plum Pudding Model
Thomson proposed the "plum pudding" model of atoms. The model showed positively charged mass with budding negative charge. -
Proof of Atom existence
Albert Einstein speculated that light energy can be absorbed in discrete packets called quanta, (led to quantum theory) Einstein also explained the equivalency of mass and energy, e=mc2 which helped determine the average distance an atom could travel -
Alpha Particles
Geiger created the Geiger Counter which measures radiation and counts atomic particles and created a counter for alpha particles which inspired Rutherford's gold-foil experiment. -
Millikan
created microscopic oil droplets which allowed him to identify charges of specific oil drops -
Rutherford Gold-Foil Experiment
created the gold-foil experiment which used a beam of positively charged alpha particles. Concluded that atoms were mostly empty space with a small positive nucleus -
Atomic Number and Periodic Table
Mosely proposed modern periodic table,
arranged periodic table in order of atomic number instead of mass, came up with periodic law, and created atomic number -
Bohr's Model
the atomic model showed electrons moving around the nucleus in orbits called electron clouds -
WWI
WWI began -
de Broglie's Hypothesis
discovered that electrons had a dual nature-similar to both particles and waves -
Schrödinger's Wave Model/ Electron Configuration
electrons only have certain probabilities of being located in the electron cloud, orbitals are described regions of a high probability of locating an electron. He also created electron configuration s,p,d,f. -
Heinsenberg's Uncertainty Principle
created uncertainty principle (impossible to know position and velocity of an electron) and theory of quantum mechanics -
Discovery of the Neutron
Chadwick discovered a neutral atomic particle with a mass close to a proton. He discovered the neutron. -
Schrödinger's Cat
Schrödinger's cat is a paradox was created to prove that atoms exist in a state known as a superposition which means they are both decayed and not decayed at the same time.
He showed it by placing a cat in a box with a Geiger counter, a vial of poison, a hammer, and a radioactive substance. A series of events occur that would eventually kill the cat. Since observer doesn't know whether the cat is alive or not and the cat is considered both alive and dead at the same time until it is observed. -
Einstien's Letter
Einstien along with scientist Leo Slizardencouraged TDR to create atomic bombs using the research he discovered years before -
Particle Theory
Physics Professor, Leonard Susskind made contributions to the Particle Theory bridging the rift between quantum mechanics that accurately describes the motion of subatomic particles and Einstein's theory of relativity that describes the forces that shape cosmic space and time. -
String Theory
Physics Professor Leonard Susskind also discovered/explored the possibility that basic building blocks of matter are not tiny points or spheres but may better be described as tiny vibrating strings. -
Peter Higgs Discovery
Discovered a sub-sub atomic particle called Higgs boson