-
In 440 BCE, Democritus said that an atom was a particle that couldn't be cut in half. He said that atoms were small, hard particles.
-
Dalton said that all substances are made of atoms, and that atoms couldn't be created, divided, or destroyed. Atoms of the same element are exactly alike. Atoms join to make new substances.
-
He said that there are particles inside atoms. He discovered that electrons were in atoms. He the the Plum Pudding Model.
-
He studied the parts of an atom, and discovered that some went through some materials, and some did not. He used the Shooting Gallery Model.
-
He discovered that electrons move around the nucleus in a certain path. He used the Electron Levels .
-
He discovered neutrons using the Beryllium and Hydrogen model.
