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400 BCE
Democritus
He described matter and his description of matter stated that it was made of small indivisible particles called atoms. He had no experimental evidence though. -
John Dalton
He discovered four things that provided experimental evidence for the atom; first, he discovered that all elements are composed of indivisible atoms. Second, he discovered that atoms of the same element are exactly alike and atoms of one element are different from those of another element and he discovered that compounds are formed when two or more atoms are chemically joined. Finally, he discovered that in a chemical reaction atoms are rearranged but not charged. -
J.J. Thomson
J.J. Thomson's model helped him discover the electron. He discovers that atoms are divisible and that there are negative particles in an atom (electrons). Scientists use this discovery to assume that there are positively charged parts of the atom and he discovered that the electron was much smaller. -
Ernest Rutherford
He discovered a very small, very dense positively charged part of the atom (nucleus). He also discovers that atoms are mostly empty space and that electrons move randomly in atoms. -
Niels Bohr
His model helped explain why electrons don't fall into the nucleus. The model shows that the Laws of Physics on our scale don't act the same on an atomic scale. It also showed electrons behaving like waves and particles. -
Erwin Schrödinger
He made the quantum mechanical model of the atom based on Bohr's model and took it one step forward. He used mathematical equations to describe the likelihood of finding an electron in a certain position.