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Greek Era: Democritus
Materialist philosopher Democritus states that all matter is made up of indivisble and unchangeable units called atomos (Greek for "uncuttable"). Democritus would then explain that though these atomos were composed of the same matter, their different shapes and sizes determine the existence of various substances and minerals. -
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Ancient India: Kanada
Much like Democritus's theory of atomic structure, Kanada proposed the idea that matter was made up of a finite number of atoms that are indivisible and eternal. Kanada also believed that atoms made up the elements earth, water, fire, and air and that these elements make up all other matter. -
Antoine Lavoisier (1743-1794)
Known as the "Father of Modern Chemistry" Lavoisier discovered that water was composed of hydrogen and oxygen. Lavoisier also explained that the elements of a chemical can not be created or destroyed, but combined into different compounds due to chemical reactions. -
Joseph Proust
In 1799 Proust developed the law of Constant Comnposition/ Law of Proportion which says that a pure compound will always have the same mass ratio of elements. -
Dalton's Model
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John Dalton
In 1803 Dalton "rediscovered" the concept of an atom being an indivisible part of matter, he would go on to think of an atom as a solid sphere. Dalton would expand on Proust's idea of Constant Composition to explain the law of Multiple Proportions and would later create 5 "principles" that govern Atomic Theory. -
JJ Thomson
Thomson developed the Plum Pudding Model which showed electrons floating in a "sea of posotive space" -
JJ Thomson
Thomson conducted an experiment using a cathode ray to prove that opposites always attract while like charges repel and during his experiment he discovered that the particles inside the cathode ray were negative because the ray moved away from the negative magnetic field. Thomson discovered a particle that was 2000 times smaller than hydrogen which is the smallest atom. He would then go to call this new particle the Electron. -
Rutherford's Model
Rutherford then created a new model of an atom with a posotive center called the nucleus which was surrounded by a sea of electrons. -
Rutherford:Gold Foil Experiment
In 1911 Rutherford conducted the Gold Foil experiment to prove his theory that if there was a negative particle then there must be posotive particles within Thomson's model. Rutherford used the recently discovered Alpha particle to observe how the particles would react to a thin sheet of gold atoms. Rutherford's experiment didn't actually discover the pronton, just that there was a posostive charge in the center. -
James Chadwick
Discovers the neutron. -
Niels Bohr
Bohr proposed that electrons travel in orbits or energy levels around the nucleus much like how the earth rotates around the sun. Bohr also said that electrons behaved as both particles and waves as they travel around the nucleus and in order for the electron to move from level to level it uses enegry which puts the electron in an excited state but this reaction is unstable and the electron will fall back into a lower level giving off the extra energy. -
Schroedinger & Heisenberg
Schroedinger and Heisenberg proposed that there is no way to really know where an electron exactly is inside an atom because electrons travel in completely random motions. Their new model is based on clouds of electron probability which mathematically tell us where an electron is most likely to be found at any point in time. -
God Particle Found
Scientist discover what they say are consistant to the Higgs boson.
