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Democritus
He started the theory of atom.His mentor was his teacher Leucippus.Democritus knew that if you took a stone and cut it in half, each half had the same properties as the original stone. He wondered that if you continue to cut the stone into smaller pieces, at some point you would reach a piece so small and that's why he called them indivisible.He hypothesized that atoms are cannot be destroyed,differ in size,shape and temperature,always moving.He believed that there are infinite numbers of atoms. -
John Dalton
Dalton's atomic theory said that elements formed by tiny particles called atoms.It states that all atoms of an element are identical.All the atoms that make up the element have the same mass.All elements weight,mass and chemical properties are diiferent and atoms are cannot be created.His atomic theory stated the general information on the atom. Everything is made of atoms. -
J.J. Thomson
Thomson discovered the Plum Pudding Model of Atom.He found electron.He used a cathode ray tube to discover the electron.When Thomson fired up the tube, he saw a ray of light between the two electrodes. To figure out what they were, he applied a magnetic field and found out that the ray moved toward a positive charge and away from a negative charge.He noticed that an atom can be divided. Also, he concluded atoms are made of protons and electrons. -
Ernest Rutherford
The Rutherford model of the atom is the classic model of the atom.Rutherford conducted his famous gold foil experiment with his colleague friend Hans Geiger.They bombarded a gold foil with positive charged alpha particles.They hypothesized that there was something positive and they called that positive force nucleus.The Rutherford Model created based on nucleus. -
Niels Bohr
Bohr's model was so successful but it only worked for first 20 elements.His model was based on Rutherford's discovery of nucleus.Different from Rutherford,he stated that electrons arranged on their shells around the nucleus.With his model,he explained how electrons could jump one to another. -
Modern Atomic Theory
Electrons are in constant motion around the nucleus,protons and neutrons are moving in the nucleus.Different from Bohr or Rutherford's model,in this atomic theory,electrons look more like clouds than orbits.The founders of this model are Erwin Schrodinger, Werner Heisenberg etc. -
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History of Atomic Theories
