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Period: 460 BCE to 370 BCE
Democritus
He developed the theory of atoms, and basically said that everything was made out of atoms. -
Period: 384 BCE to 322 BCE
Aristotle
He believed in 4 elements, earth, air, fire, and water.
In addition to believing in the four elements, he also believed that they combined to produce all substances around us. -
Period: 300 BCE to 700 BCE
Alchemy
Alchemy is the study and philosophy of how to change basic substances into other substances. Alchemy was based on the belief that there are four basic elements in nature: air, fire, water and earth. The people who practiced it mainly wanted to turn lead into gold. Some looked into the more spiritual side of alchemy. vitalism holds that living things contain some fluid, or a distinctive ‘spirit’. -
Period: to
Anton Laurent de La Voisier
He was a French nobleman and chemist. Lavoisier analysed air into two constituents. Oxygen and nitrogen. He also discovered the law of conservation of mass. He died from getting beheaded in the French Revolution. -
Period: to
Benjamin Franklin
Benjamin Franklin discovered that electrical charges come in 2 varieties – positive and negative and that like charges repel, opposite charges attract. -
Period: to
Joseph Louis Proust
Joseph Louis Proust was a French chemist. He was best known for his discovery of the law of constant composition in 1794. The law of constant composition states that a chemical compound always contains exactly the same proportion of elements by mass. -
Period: to
John Dalton
He was the father of the atomic theory. His theory stated that matter is made up of atoms that are indivisible and indestructible, all atoms of an element are identical, atoms of different elements have different weights and different chemical properties, atoms of different elements combine in simple whole numbers to form compounds, and atoms cannot be created or destroyed. -
Period: to
William Crookes
William Crookes was a British chemist and physicist. He invented the cathode ray tube. It was a glass tube that is evacuated and coated with fluorescent paint and when it’s connected to a battery, the paint glows, indicating that there is some type of radiation streaming from the battery. When Crookes placed a paddle wheel in the cathode ray tube and turned on the battery, the wheel spun and since the tube was evacuated, this told Crookes that the Cathode Ray has mass. -
Period: to
Sir John Joseph Thomson
He continued experimenting on the CRT, JJ Thomson used charged plates to deflect the cathode ray. Found the ray deflected away from the negative plate, and toward the positive. He deduced that the cathode ray was made of negative particles. He named them electrons. -
Period: to
Pierre and Marie Curie
Pierre and Marie Curie are best known for their pioneering work in the study of radioactivity, which led to their discovery in 1898 of the elements radium and polonium from uranium ores. -
Period: to
Becquerel
He discovered radioactivity in Uranium ore. In 1903 he shared the Nobel Prize for Physics with Pierre and Marie Curie. -
Period: to
Millikan
He calculated the mass and charge of an electron. -
Period: to
Ernest Rutherford
He classified radiation. He aimed a ray of alpha radiation at the foil, and expected that the alpha rays would pass right through the metal atoms in the foil, and the fluorescent coating would light up right behind the foil. He came to the conclusion that atoms are mostly empty space, there must be a solid core in the center of the atom, and the core must be positively charged, since it deflected an alpha ray. -
Period: to
James Chadwick
He proved the existence of another subatomic particle, that had no charge, and named it the neutron.