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460 BCE
Democritus’ Atomos Argument
Democritus (460 BCE - 370 BCE) argued that everything should be composed of tiny pieces of pure substances called atomos. These atomos -
384 BCE
Aristotle’s Element Argument
Aristotle disagreed with Democritus’ idea of atomos and instead proposed that everything was made of four elements: air, earth, water, and fire. These elements were always in balance. -
Period: 1214 to 1292
Roger Bacon
Roger Bacon was known for experimenting with and noting the explosive properties of gunpowder, as well as creating a formula to create gunpowder. -
Period: 1561 to
Sir Francis Bacon
Francis Bacon preferred inductive logic over naturalistic study, as he believed deductive logic relied on syllogism, which required factual evidence. He eventually brought the scientific method to light. -
Period: to
Robert Boyle, Esq.
Robert Boyle was known for writing “The Skeptical Chymist”. He valued doubt because it made room for experimentation. He also believed that there were more than four elements, and changed the definition of an element to “simple or perfectly unmixed bodies”. -
Period: to
Antoine Lavoisier
Lavoisier performed systematic experiments and recorded observations. Lavoisier was known as the “Father of Chemistry”. He compiled works of many early chemists into one textbook for future chemists to use. He was also known for proposing the Law of Conservation of Mass. -
Joseph Proust
Proust was responsible for the Law of Definite Proportions. His law was exclusively concerned with inorganic binary compounds, such as metallic oxides, sulfides, and sulfates. -
Alessandro Volta
Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and copper. This discovery led to the creation of the first electric battery and the first continuous electric current. -
Period: to
Justus von Liebig
Liebig invented a contraption to demonstrate combustion. Combustion separated elements. -
John Dalton
Dalton was famous for his discovery of the Atomic Theory and its 5 points. He based the theory off of Lavoisier’s work and was inspired by Democritus. -
Dmitri Mendeleev
Mendeleev was a Russian chemist who created the first periodic table. He also discovered that organizing the elements by atomic weight revealed a periodic trend in certain elements. -
Eugene Goldstein
Goldstein discovered that atoms have positive and negative charge potential through the use of a Crooks tube. -
Antoine Henri Becquerel
Becquerel placed uranium salts and photographic plates in a drawer due to sub-optimal weather conditions, as he required sunlight for his experiment of radiation to work. However, on March 1st, he discovered that the plates produced images nonetheless, and therefore discovered radioactivity. -
JJ Thomson
Through the use of the cathode ray tube, Thomson discovered electrons; subatomic particles within atoms. This therefore debunked Dalton’s theory that atoms were the smallest forms of matter. He created a plum pudding model that demonstrated that atoms were mostly positively charged with negative particles scattered around the atom. -
Marie and Pierre Curie
Marie and Pierre were known for discovering two new radioactive elements: radium and polonium. -
Ernest Rutherford
Rutherford is famous for his gold foil experiment, in which he shot alpha particles at gold foil. The expectation was for all particles to penetrate the foil, but some particles were deflected. This completely changed their current view of the atom. This experiment disproved the plum pudding model made by JJ Thomson. -
Robert Millikan
Millikan used the oil drop experiment to determine the mass of the electron. -
Henry Moseley
Moseley conducted experiments to prove that:
1. An element is determined by atomic number, not atomic weight.
2. The atomic number is the # of protons in the nucleus. -
James Chadwick
Chadwick bombarded Beryllium atoms with alpha radiation. This revealed an entirely new subatomic particle; the neutron.