-
Period: 460 BCE to 370 BCE
Democritus
He called small particles of matter atomos . He used his Greek roots to help him come up with the definition of atoms -
Period: 384 BCE to 322 BCE
Aristotle
A Greek that there were four elements that everything was made up of : earth, water, air, and fire -
Period: 300 BCE to 700
Alchemy pt.1
Alexander the Great conquered Egypt. As a result khemia , Greek word for Egypt. The word alchemy came from the word khemia , which means Egypt. Arabs occupied Egypt and further developed the science spread it to the west (Spain) in 700s. Alchemists applied this concept of purification and search for perfection to human conditions. In the 16th century , alchemist in Europe had separated into 2 groups. -
Period: 600 to 700
Alchemy pt.2
West Alchemist focused on the discovery of new compounds, reactions , and chemical processes- leading to what is now science of chemistry they invented distillation, percolation , extraction , rudimentary chromatography. The 2nd group looked at spiritual, metaphysical side of alchemy, the search for immortality and transmutation of base metals into gold . Led to modern day idea of alchemy. -
Period: to
Vitalism
Living organisms are different from non living entities because it contains a vital spirit. Living things are thus governed by different principles than are inanimate things -
Period: to
The phlogiston theory
Ancient Greek word for “burning up” stand in 1667 by johann becher. Postulated the existence of fire like elements called “phlogiston”that contained within combustible bodies and released during combustion. A substance that did burn because it contained phlogiston. Carbon dioxide no longer capable of burning was called “dephologsticated air” -
Period: to
Anton Laurent de la voisier
Father of modern chemistry because he relied on quantitative observation to develop conclusions . He dispelled the phlogiston theory by proving that oxygen causes combustion. He discovered the laws of conservation of mass , by proving that the mass of metal is the mass of the metal plus oxygen when the metal oxide decomposes. Matter can change form but can’t be created or destroyed in a chemical reaction -
Period: to
Benjamin Franklin
Discovered that electrical charges come in varies - positive and negative. Likes charges repel , opposite charges attract -
Period: to
Joseph Louis Proust
Law of definite proportions , sometimes called the law of constitutional composition, which dates that compound always contains exactly the same proportion of elements by mass H2O always contains 88.9 % O. 11.1 by mass -
Period: to
John dalton
His theory of atomic matter : 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 . Atoms can’t be created or destroyed. When a compound decomposes , the atoms are recovered unchanged -
Period: to
William Crookes
He discovered the element thallium Andy invented the radiometer , the spinthariscope , and the Crookes tube a glass tube that is evacuated coated with fluorescent paint. What connected to a battery , the most paint glows , indicating that there is some type of radiation streaming from the battery. -
Sir John Joseph Thompson
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. Deduced that the cathode ray was made of:
Negative particles. He named them electrons. -
Period: to
Ernest Rutherford Part 1
What he did:
Stretched a sheet of gold foil in a tin can and coated the inside of the can with fluorescent paint.
Aimed a ray of alpha radiation (+ charges) at the foil.
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.
What he observed:
There must be a solid core in the center of the atom.
The core must be positively charged, since it deflected an alpha ray -
Curies (Marie and Pierre)
Discovered and isolated polonium and radium from uranium ores -
Becquerel
Discovered radioactivity in Uranium ore -
Milikan
Calculated the mass and charge of an electron
Robert Andrews Millikan was an American experimental physicist honored with the Nobel Prize for Physics in 1923 -
James Chadwick
Discovered the neutron Won Nobel Prize in 1935
In 1941, he wrote the final draft of the MAUD Report, which inspired the U.S. government to begin serious atomic bomb research efforts.
He was the head of the British team that worked on the Manhattan Project during the Second World War.
He was knighted in England in 1945 for his achievements in physics.