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400
Artistole
Artostole was born in 384 BCE in Stagira, Greece.
He lived in Stagira, then Athena,where he studied and found his own school, then Chalcis where he died in 322 BC.
Aristotle did not believe in the atomic theory and he taught so otherwise. He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. -
460
Democritus
Democritus was born in 460 BCE in Abdera, Greece. He died in 370 AD. Democritus Atom theory was that. He asked, if you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? The atom itself didn't change, but it moved around in various spaces. -
John Dalton
John Dalton was born on September 6 1766 and died July 27 1844 in the UK. He was an English chemist, meteorologist and physicist. His atomic theory was that:
1- all matter is made of atoms, which are indivisible and indistructable.
2- all atoms of an element are identical in mass and property.
3- compounds are formed by a combination of two or more different kinds of atoms.
4- all matter consists of tiny particles. -
Dmitri Mendeleev
Dmitri Mendeleev was born February 8, 1834 and died February 2, 1907 in Russia. was a Russian chemist and inventor. He formulated the Periodic Law, created his own version of the periodic table of elements, and used it to correct the properties of some already discovered elements and also to predict the properties of eight elements yet to be discovered. -
Henri Becquerel
Henri Becquerel was born December 15, 1852 and died August 25, 1908 in France. He was the discoverer of radioactivity along with Marie Skłodowska-Curie and Pierre Curie, for which all three won the 1903 Nobel Prize in Physics. After conducting an experiment with the exposure of a uranium bearing crystal to sunlight, Becquerel discovered that a piece of mineral which contained uranium could produce its image on a photographic plate in light. This led to his discovery of radioactivity. -
J.J Thomson
J.J Thompson was born December 18, 1856 and died August 30, 1940 in the UK. He was the one who discovred the electron. He discovered that through conducting an experiment in which he realized that he could deflect the cathode rays in an electric field produced by a pair of metal plates. That experiment led to the discovery of the electron in 1897 which meant that the atom can be split into even smaller parts. His discovery was the first step to a detailed model of an atom. -
Hantaro Nagaoka
Hantaro Nagaoka was born on August 15, 1865 and died December 11, 1950 in Japan. He was a Japanese physicist and a pioneer of Japanese physics during the Meiji period. Nagaoka disagreed with Thomson's theory and was the first to propose the idea that negatively-charged electrons are located on the outside of the atom. -
Marie Curie
Marie Curie was born on November 7, 1867 in Poland and died July 4, 1934 in France. She was a Polish and naturalized-French physicist and chemist who conducted pioneering research on radioactivity. She discovered polonium and radium with her husband Pierre Curie. They had the same idea as Henri Bequerel, just expanced and improved. -
Ernest Rutherford
Ernest Rutherford was born on August 30, 1871 in New Zealand
and died October 19, 1937 in the UK. He was a consummate experimentalist, He discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei. -
Niels Bohr
Niels Bohr was born on October 7, 1885 and died November 18, 1962 in Denmark. He was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory. Bohr developed the Bohr model of the atom, where he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level to another. -
James Chadwick
James Chadwick was born October 20, 1891 and died July 24, 1974 in the UK. He was an English physicist who was awarded with the Nobel Prize for discovering the neutron. Chadwick did a test on Beryllium and bombarded the element with alpha particles. This caused some of the protons to be discharged which led to the discovery of creating neutrons.
