Here's a breakdown:
* Ancient Greeks: Philosophers like Democritus and Leucippus proposed the idea of atoms, but they didn't have any experimental evidence to support it.
* John Dalton (1803): Dalton proposed the atomic theory, which was based on experimental observations. His theory stated that:
* All matter is made up of tiny, indivisible particles called atoms.
* Atoms of a given element are identical in size, mass, and properties.
* Atoms cannot be created or destroyed, only rearranged.
* Atoms of different elements combine in simple whole-number ratios to form compounds.
* Later Developments: Dalton's atomic theory was later refined and expanded by scientists like J.J. Thomson, Ernest Rutherford, and Niels Bohr, who discovered the structure of the atom and its subatomic particles.
Therefore, while the concept of atoms existed before Dalton, it was his atomic theory, supported by scientific evidence, that solidified the idea that all things are made of atoms.
