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460 BCE
Democritus
Argued that everything is make up of tiny particles of pure substances called atoms. -
384 BCE
Aristotle
Believed everything is made up of four elements: Earth, air, fire, and water. -
1257
Roger Bacon
Experimented with gunpowder.
He wrote how to create gunpowder and the detailed formula of it. -
Period: to
Robert Boyle
Wrote "The Skeptical Chymist"
He doubted experiments so they would be designed and tested. Also thought there to be more than four elements. Actually redefined the word "atom" to be "simple or perfectly mingled bodies" -
Period: to
Sir Francis Bacon
Proposed inductive logic to be preferred over deductive logic for more naturalistic studies. Inductive login makes room for conclusions based on incomplete evidence. -
Antoine Lavoisier
"Father of modern Chemistry"
Created the first chemistry textbook by:
performing systematic experiments, recording observations, and comparing them with the work of other scientists. -
Period: to
Justus Von Liebig
Developed complicated ways to find the amount of carbon, oxygen, and nitrogen in organic chemical compounds. -
Alessandro Volta
Invented the voltaic pile, which was one of the first batteries.
Volta first called the battery "The Artificial Electric Organ" because it was such a new invention. It was a stack of alternating metal discs separated by just material that was brine-soaked. The material helped make the battery more electric. -
Joseph Proust
Proposed Law of Definite Proportions. Which is chemical compounds are formed in constant, defined ratios of elements, which are determined by mass. -
John Dalton
Developed 5 points of an Atomic Theory.
considered laws, Law of the Conservation of Mass, Law of Definite Proportions, and Law of Multiple Proportions. -
Dimitri Mendeleev
Created the first periodic table.
Arranging them first by relative mass, then secondarily by affinity, reactivity, and physical properties. -
Eugen Goldstein
Found that atoms have a positive and negative charge. He found this with experimenting with a Crooks tube. -
Henri Becquerel
Discovered radioactivity by using naturally fluorescent minerals.
experimenting with the X-ray which had been invented the year before. exposing potassium uranyl sulfate to the sun, then wrapped this in back paper. He thought the experiments had failed, but concluded in clear images. -
J.J. Thomson
discovered that electrons exist as part of all atoms and are negativly charged.
Proposed the model of an atom as "plum pudding" -
Period: to
Ernest Rutherford
Suggested the existence of the proton.
performed the "gold foil" experiment. with the conclusions of the atoms in that experiment, Rutherford had to change the model of atom. J.J. Thomson's atomic model had been proven wrong. -
Robert Millikan
Demonstrated the charge of one electron.
Dropped small drops of oil between two metal plates and calculated their mass. -
Henry Moseley
Wrote a paper concluding the atomic number is the number of positive charges in the atomic nucleus. -
Period: to
James Chadwick
Discovered the neutron.
He performed repeated experiments with beryllium atoms with alpha radiation. He found evidence of a kind of radiation, the neutron.