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460
Democritus
Democritus said “everything is composed of atoms” and “between atoms, there lies empty space; that atoms are indestructible, the more any indivisible exceeds, the heavier it is." -
John Dalton
John Dalton discovered all matter is composed of atoms,
atoms of each elements are the same size,mass,etc. but are different from atoms of other elements,
atoms can’t be destroyed,
atoms are ‘tiny solid balls," -
J.J Thompson
Discovered that all matter is made up of tiny particles that are much smaller than atoms they were
originally called called these particles “corpuscles”
now called electrons -
Robert Milliken
Milliken measured the charge of electrons
The mass of an electron is at least 1000 times smaller than the lightest atom. -
Ernest Rutherford
Ernest prefromed the gold foil experiment that shows the atoms has a tiny, heavy nucleus. -
Neils Bohr
He found a positive charge nucleus,
surrounded by electrons that travel in circular orbits around the nucleus which is similar to solar system -
James Chadwick
He bombarded beryllium atoms with alpha particles which
became known as the nucleus
