Very many, and much to say about all of them. Try these in Wikipedia for a start: Aristotle, Dalton, Rutherford, Geiger and Marsden, Chadwick, Bohr.
he found the measurement or electron charge
Leucippus and Democritus have proposed intuitively the existence of atoms approx. 2 450 years ago. This wasn't an experimental discovery. They were philosophers not chemists.
the chemists goal is to understand the atoms that compose it
Noble gases explain the stable behavior of any element and hence enhances the concept of atom's structure.
His MAJOR discovery was when he discovered the atom.
This is a problem of atomic physics !
discovery of the atom's structure
the ancient Greeks made the atom, but they had no proof after the discovery.
Well astronomers as well as physicists, chemists, and even biologists. They all contribute to astronomy in their own respective ways.
Its RADIOACTIVITY!! That was the first discovery that rejects the idea that the atom is indestructible
1898
Its itself