-
465
Democritus
Democritus discovered explained his theory of the atom with 5 main points:
1.All matter consists of invisible particles called atoms
2. Atoms are indestructible
3. Atoms are solid, although invisible
4. Atoms are homogenous
5. Atoms differ in size, shape, mass, position, and and arrangement.
Democritus believed that atoms were always moving and that there was an infinite amount of them. -
John Dalton
John Dalton's research rendered 4 major points of the atom, which either agreed with Democritus's ideas or built upon them. They were:
1. All matter is made of atoms. Atoms are indivisible and indestructible
2. All atoms of a given element are identical in mass and properties
3. Compounds are formed by a combination of two or more different kinds of atoms.
4. A chemical reaction is a rearrangement of atoms.
Dalton also found that gasses could only be combined in certain proportions -
J.J. Thomson
Thomson discovered the existance of the electron by experimenting with a cathode ray tube. Also, he discoved isotopes in a large number of non-radioactive elements. Incorrectly, however, Thomson believed that the mass of an atom was even distributed. -
Ernest Rutherfod
Rutherford disproved Thomson's idea that the mass of an atom was evenly distributed throughout. Instead, using his gold foil experiment, he proved that the mass was concentrated in the atom's nucleus. -
Robert Milliken
Milliken concluded that atoms contained a negatively chraged particle with significantly less weight than a hydrogen atom. He later determined that electrons have a fixed charge and, using his famous oil-drop experiment, he was able to determine the mass of an electron. -
Niels Bohr
Bohr found that atoms travel in separate orbits around the nucleus, Also, that the number of electrons in the outer orbit determined the properties of the element. -
James Chadwick
Chadwick discovered a neutral atomic particle: The nuetron.
