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450
Democritus 450 B.C.
Developed the idea of atoms. Democritus created the atom so everyone believed him. He was born in 460 BC and died in 370 BC. -
John Dalton
Dalton stated that elements are made of particles called atoms.All atoms of a particular element are going to be identical.Atoms of different elements will be different.Atoms combine to form compounds. Atoms cannot be created or destroyed only changed. He was born in 1766 and died in 1844. -
JJ Thomson
Peformed the Cathode Ray Tube expierement. The atom was made of negative particles. He was born in 1856 and died in 1940. -
Marie and Pierre Curie
They established that the heavy element thorium was radioactive and discovered two new elements: polonium and radium. They refined techniques for extracting radium from ores. Marie was born 127 and died in 1907. Pierre was born in 1859 and died in 1906. -
Henri Becquerel
A French physicist who found that rays coming from a uranium ore affected a photographic plate like X-rays did.The rays were not from an external source and were morepowerful than those from a sample of pure uranium. Hisexperiment led to the discovery of natural radioactivity. He was born in 1852 and died in 1908. -
Robert Millikan
He discovered the charge of an electron. Did the oil drop experiment. They wanted to measure the elementary electric charge.He was born in 1868 and died in 1953. -
Ernest Rutherford
Inferred a small, dense, positively-charged nucleus as theresult of the alpha particle scattering gold foil experiment. Ernest was born in 1871 and died in 1937. -
Neils Bohr
He expierimented with atomic spectrum of hydrogen called the Planatary Model. He was born in 1885 and died in 1962. -
James Chadwick
Chadwick discovered the neutron and recieved many awards for his accomplishments. Did a type of radiation that contained high energy photons. Chadwick was born in 1891 and died in 1974. -
Quantum Model
The Quantum model is the model used today. It was developed by Werner Heisenburg. -
Aristotle
Developed methods for the gathering of scientific fact.His work provided the basis for scientific work more than amillenium. He was born in 384 BC and died 322 BC.
