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460 BCE
DEMOCRITUS
Democritus was a Greek philosopher who suggested the atomic theory by explaining that all things are "composed of minute, invisible, indestructible particles of pure matter which move about eternally in infinite empty." -
384 BCE
ARISTOTLE
A Greek philosopher who did not believe in the atomic theory. He thought that all things were made out of four elements, Earth, Fire, Water, and Air. He got the brain storm rolling when it comes to atoms and what objects and humans are made of. He believed every form contained one of these elements. -
ANTOINE LAVOISIER
Antoine was a French chemist that contributed to the atomic theory through a series of experiments which found that the total mass of products and reactants in a chemical reactions is always the same. His contribution led to the law of conservation mass. -
JOHN DALTON
John Dalton was a British schoolmaster in the 19th century he is known for making inferences on how atoms bond together in definite proportions. The tests that he ran was measuring the proportions of hydrogen to oxygen in different amount of the substances, since the ratios were the same he was able to conclude that atoms of different elements combine in whole number ratios -
JOSEPH LOUIS PROUST
Joseph Louis's contributed to the atomic theory when he summarized and observed that chemical compounds are formed of constant and defined ratios of elements, as determined by mass. -
MICHAEL FARADAY
Michael led to the idea that atoms had an electrical component. He placed two opposite electrodes in a solution of water containing a dissolved compound. He concluded that one of the elements of the dissolved compound had accumulated on one electrode, and the other element was deposited on the opposite electrode. His final analysis concludes that electrical forces were responsible for the joining of atoms in compounds. -
J.J THOMSON
Thomson conducted an experiment where he took athode ray tubes that showed that all atoms contain tiny negatively charged subatomic particles or electrons -
HENRI BECQUEREL
Henri contributed to the discovery of radioactivity in uranium. He also forced scientists to change their ideas about atomic structure. -
MARIE AND PIERRE CURIE
Marie was a polish-French physicist/chemist and Pierre also, both married. Their contribution was in Marie's experiment where she experimented on uranium rays and discovered that they remained constant, no matter the condition or form of the uranium. The rays came from the element's atomic structure. -
MAX PLANCK
Max was a German physicist and is best known for being the originator of the quantum theory of energy. HIs work directly contributed to the understanding of atomic and subatomic processes. His work in work in thermodynamics led to the formulas of his quantum theory. -
ALBERT EINSTEIN
The most famous scientist and his contribution to atomic theory involved math which could prove the existence of atoms. This helped revolutionize all the sciences through the use of statistics and probability math. -
ROBERT MILLIKAN
Robert was an American physicist who began a series of experiments relatively focused on electric charge carried by a single electron. He discovered this by doing the "falling-drop" method. This resulted in the atomic structure of electricity. -
ERNEST RUTHERFORD
Ernest's contribution is from his studies in radioactivity and atoms. He discovered that there are two types of radiation, alpha and beta particles, which come from uranium. He discovered that atoms consist of primary empty space with a mass in a central positively charged nucleus -
NEILS BOHR
Danish psychist who introduced a theory for the hydrogen atom based on the quantum theory he said energy is transferred only in certain quantities. Electrons should move around the nucleus but only in certain orbits, When jumping from one orbit to another with lower energy, a light quantum is release -
JAMES CHADWICK
James contributed to the atomic theory when he discovered the neutron in atoms.