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400
400BC- Democritus
Democritus was an ancient greek philosopher who was bron in Abdera,Thrace, Greece. In 400 BC, he proposed the idea that matter is created by small pieces, that couldn't be broken down into even smaller pieces. He called the smallest peice of matter an Atom. -
!808- John Dalton
John Dalton, an English Chemist, suggested a similar idea to that of Democritus however his theory was based upon evidence. Dalton's Theory comprised that an atom is an industructable particle, and that all elements consisted of atoms. He also said that a chemical reaction is seen as a rearrangment of atoms, and that compounds are a mix of either two elements or atoms. His theory was also based from the findings of Lavoisier and Proust. -
1897- Joseph John Thomson
Joseph John Thomson, born 1856 and died 1940, a professor of experimental physics, discovered today as what we know as electrons. He declared that atoms were made up of even smaller particles called electrons. He conducted several experiments and tests, and proved to scientists that his theory was right. -
1911- Ernest Rutherford
Ernest Rutherford, was a New Zealand born english chemist and physicist. He developed the theory that describing the atom of having a central positive Nucleus, that were encircled by negative orbiting electrons. Rutherford discovered this by conducting his Gold Foil experiment. Shooting alpha particles, which are really small positive charged particles into a thin sheet of foil. A great no. of the particles went through but but 1 in 8000 were deflected. The atom was mostly emptyjust "Empty Space -
1913- Niels Bohr
Niels Bohr, a Danish physicist, proposed the idea of the quantum theory. His theory was based on Rutherford's atomic model, but based his theory that over Rutherfords. He stated that electrons in an atom revolve around the atom's nucleus, only in seperate orbits with no other orrbits being possible. Furthermore, he said that the outer orbits determine the atoms chemical property and that outer orbits hold more electrons than the inner. As a result of testing, he created a new atomic model. -
1932- James Chadwick
James Chandwick, born a englishman and physicist by profession, made a discovery in nuclear science. After many countless experiments and tests, his theory was that an atom would have a neutron. He also developed the idea that that the atomic number is resulted by the number protons within an atom. Later, he did discover fourth subatomic particle, being the neutron, and this is what made him most recognizable.
