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460 BCE
Democritus
Was the first person to use the name atom. He proposed all atoms were small and hard particles made out of 1 type of material. He also said that atoms were always moving and joined together to form a variety of materials. -
384 BCE
Aristoteles
He was against Democritus statements. He didn't believe that the atom was invisible and denied the existence of the atom. -
John Dalton
He created the atomic theory which stated the basic laws of atoms -
J.J Thompson
He discovered an error in Daltons’s theory and proved that inside the atom exists even smaller particles. He theorized that there was a positive charge that he couldn't identify ,also that electrons had a negative charge. -
Millikan
Determined mass of an electron, and confirmed that they have a negative charge and were present in all atoms -
Ernest Rutherford
Experimented with a positive charged ray threw a gold plate.
He proposed a new model for every part of the atom. -
Neils Bohr
Stated that electrons are in orbits. Defined the energy states of electrons. -
Henry Mosely
He discovered that the atomic number is the same as the number of protons and also discovered that atoms of same element have a unique positive charge in their nucleus -
James Chadwick
He discovered the neutron and determined neutrons have the same mass as a proton and that it isn't charged -
Erwin Schrodinger & Werner Heisenberg
Created the quantum mechanical model that stated that electrons that travel in orbits but in orbitals