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400 BCE
Democritus
Democritus disproves Aristotle's theory that all matters are infinitely divisable - he named these tiny building blocks (at the time) Atomos. Democritus also introduces the concept that the atom is the basic building block of all matter. He claims that atoms are indivisible. He presented them as a plain grey sphere. -
Lavoisier
Antoine Lavoisier created the theory that - not matter what shape they take - atoms of the same kind will always have the same mass. -
Dalton
John dalton then discovered that all atoms of the same element look the same, atoms cannot be made or destroyed, atoms of different elements have different colours and masses, and that atoms can form atom compounds. -
J.J Thomison
J.J Thomison discovered the plum pudding model and that all atoms have negatively charged sub-atomic particles (electrons) - and were surrounded in a positively charged lining. -
Einstein/ Brown
During 1827, In an experiment where Robert Brown analysed some pollen, he noticed that pollen particles jiggled randomly (even when there was noting to move the pollen around). This coined his experiment the term 'Brownian motion'. During 1905, Einstein, with some calculation, proved that the minute atoms must be smacking into the pollen. -
Rutherford
Rutherford discovered the proton and that all atoms possessed a positively charged nucleus, with electrons surround. But never answered the question as to how the electrons don't become attracted to the protons... -
Bohr
Bohr discovered that the atom had shells - ring-like surrenders to the nucleus. The electrons would sit on the nucleus and not move; this explained why the negatively charged electrons would give in and attract to the protons. -
Chadwick
James Chadwick discovered that the nucleus of an atom also contained a new sub-atomic particle; the neutron. The 'neutron' belonged as the second subatomic particle in the nucleus - along side the proton.