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Democritus 460-370 BC.
460-370 BC. He was an Ancient Greek philosopher born in Abdera, Thrace, Greece. He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos. The theory of Democritus and Leucippus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms lies empty space; that atoms are indestructible have always been, and always will be, in motion. His beliefs were accepted. -
John Dalton 1766-1844
He was an English chemist, He is known for his atomic theory, laws of multiple proportions, Dalton's law of partial pressures, and Daltonism. Dalton printed his first published table of relative atomic weights. Six elements appear in this table: hydrogen, oxygen, nitrogen, carbon, sulfur, and phosphorus, He believed that all atoms of a given element are identical, elements are made of particles called atoms, and atoms cannot do created or destroyed. -
Antoine Lavoisier 1743-1794.
The "father of modern chemistry", he was a French nobleman in the histories of chemistry and biology. He stated the first version of the law of conservation of mass, recognized and named oxygen, and hydrogen. He abolished the phlogiston theory and helped construct the metric system, He wrote the first extensive list of elements, and helped to reform chemical nomenclature. He discovered that, although matter may change its form or shape, its mass always remains the same. -
Joseph Proust 1700's.
Proust is best known as a french chemist, particularly for his enunciation of the law of definite proportions. The essence of Proust’s law is that chemical substances only truly combine to form a small number of compounds, each of which is characterized by components that combine in fixed proportions by weight. His beliefs were were not at first accepted but later on were. -
J.J. Thomson 1856-1940
The British physicist Joseph John Thomson discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube. Thomson interpreted the deflection of the rays by electrically charged plates and magnets as evidence of "bodies much smaller than atoms." He calculated this as having a very large value for the charge-to-mass ratio. -
Robert Milikan 1868-1953
He was an American experimental physicist, and Nobel laureate in physics for his measurement of the charge on the electron and for his work on the photoelectric effect. in 1909 Millikan worked on an oil-drop experiment in which they measured the charge on a single electron. His experiment measured the force on tiny charged droplets of oil suspended against gravity between two metal electrodes. -
Niels Bohr 1885-1962
He was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. He was famous for his model call the bohr model, it depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus, similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity. -
Ernest Ruthefrord 1871-1937
He was a British-New Zealand chemist and physicist who became known as the father of nuclear physics.[1] In early work he discovered the concept of radioactive half life. Rutherford performed his most famous work after he received this prize. In 1911, he postulated that atoms have their positive charge concentrated in a very small nucleus & the Rutherford model, or planetary, model of the atom was born through his discovery of Rutherford scattering in his gold foil experiment. -
Aristotle 384-322 BC.
He was known for being a reliable philosopher. As a result, his ideas had a much greater impact on people. His ideas when it came to matter, however, were slightly different than his predecessor, Democritus. Aristotle believed all things were made of: matter and essence. Aristotle thought organisms of the same species were made of the same but different matter. Aristotle believed matter could be broken down into the four elements. His beliefs were accepted over democritus's.
