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500 BCE
The Alchemists
The Alchemists created the theory that matter is composed of Atoms of different weights and combine in simple ratios of weight. This theory was founded by John Dalton. -
400 BCE
Democritus
He believed that everything is composed of atoms. Also he thought that atoms have and will always be in a motion. This is where he made a theory that the universe is made up of tiny atoms. -
387 BCE
Plato
Four atomic types and purposes and fifth type he called ether. Ether explained the shapes of atoms. -
335 BCE
Aristotle
Negative influence. He believed in the four elements of earth, fire, water, and air not atoms which set back atomic theories for 2000 years. -
Robert Boyle
Father of modern chemistry. Boyles law -PV= k pressure of ideal gas constant temp. Created gas chambers to study physical changes in the atoms and elements have corpuscles that organize to create different substances. ( Composition of atoms) -
Lavoisier
developed theory about chemical reactivity of oxygen. He helped write modern system for naming chemical substances Law of Conservation of Mass= matter is not created nor destroyed in normal chemical reactions. -
John Dalton
Atoms from different elements have different weights and atoms of elements can combine to form compounds. -
Solid Sphere of Billiard ball model
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Dmitri Mendeleev
Created the Periodic Classification system. He was even smart enough to leave gaps for new elements that would be discovered after 1871 -
The Curies
Marie and Pierre Curie researched a lot on Radioactivity. Later on with their research, they discovered two new elements- Radium and Polonium. Marie found that certain atoms are in these two elements. -
Plum Pudding Model
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J.J. Thomson
His theory was atom is a sphere of positive matter and electrons are positioned by electrostatic forces positively charged particles. This led to the development of the mass spectrograph. -
Albert Einstein
Had the theory of relativity Nobel Prize to understand laws of electromagnetism. 1905 he proved the existence of atoms -
Robert Millikan
He determined that all electrons carried a charge. (Atomic structure of electricity) -
Ernest Rutherford
Ultraviolet radiation alpha and beta radioactive elements the atom is a tiny solar system. -
Neils Bohr
Bohr came up with the Atomic Model which is an positive charged atom surrounded by orbiting electrons. He also came up the the Liquid Drop theory. The Liquid Drop Theory was basically a representation of an atoms nucleus. The theory was also big in the steps of making the atomic bomb during World War Two. Bohr later invented the Solar System Model in 1915 -
Solar System Model
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Henry G.J. Moseley
Atomic number importance, not just atomic weight relationship between atomic number and the charge in the nucleus of an atom. -
Electron Cloud model
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Werner Heisenberg
Uncertainly principle that a particles position and momentum cannot both be known exactly.
