jul 30, 1803 - John Dalton
Description:
Dalton theorized that all matter is made of atoms, that atoms are invisible, and that all elements in an atom are identical to mass and properties. He also said that compounds are combinations of two or more different atoms and that a chemical reaction is just the atoms rearranging.Added to timeline:
Date:
jul 30, 1803
Now
~ 223 years ago