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Democritus
Created the first notion of the atom. Democritus argued that there were an infinite number of different types of atoms. Democritus's atomic theory represented the modern principles of the conservation of energy. -
John Dalton
John Dalton was most commonly known as the "father of atomic theory". Dalton created the first atomic theory and his five famous postulates. Dalton began an experiment called "Dalton's Atomic Theory". This theory stated the atomic theory and he concluded that atoms were actually circles. Dalton's most important contribution to science was his theory that matter is composed of atoms of differing weights. -
Henri Becquerel
Henri Becquerel is most know for his work in radioactivity. Henri Becquerel first strted his carrer studying optics, then turned to infra-red structures, and finally studied the absorbtion of light. Henri discovered this by first placing a Uranium filled crystal into the sunlight, then placing it on a photographic plate. The showed its image on the plate and Becquerel concluded that the absorbed energy of the sun was being reflected in the form of X-rays. -
J.J. Thomson
J.J. Thomson's most notable accomplishment is the discovery of the electron. He made this discovery through an experiment with the help of the cathode ray tube. Thomson found that by applying a magnetic field across the tube, there was no activity recorded by the electrometers and so the charge had been bent away by the magnet. This proved that the negative charge and the ray were inseparable. -
Marie & Pierre Curie
Made advancements in the investigation of radioavtivity. Discovered two new elements, Polonium and Radium. Used an electrometer to make radiation measurements to trace the amount of unknown radioactive elements. -
Ernest Rutherford
Ernest Rutherford's most notorius acomplishment was the descovery of the nucleus. He made his discovery through his e- cloud model. -
Niels Bohr
Niels Bohn created the planetary model of the atom. His ideas were later known as the "Bohr Model". -
Robert Millikan
Born in 1868. Discovered the charge of the electron through the oil drp experiment. Robert Millikan put a charge on a small drop of oil and measured the electric field that was needed to stop the drop of oil from falling. Then, he could calculate the force of gravity on one drop, and could therefore measure the electric charge that the oil drop had. -
James Chadwick
Born in October 1891. Founded the nuetron. James Chadwick proved the discovery of the neutron by shining a beam of radiation through a material such as paraffin, which would then detect when there were loose protons present. This was measured with a Geiger counter. -
Quantum Model
The Quantum Model is the idea of the atom that we use today.The quantum mechanical model is based on quantum theory, which says matter has properties associated with waves. -
Aristotle
Aristotle believed that the atom was the smallest piece of matter. Aristotle's idea of the atom was more popular than previous ideas because people favored his ideas over all others. There was no experiment to prove Aristotles ideas of the atom.
