Here's a breakdown:
* Early Atomic Theory: The ancient Greeks first proposed the idea of atoms, but it wasn't until the 19th century that John Dalton developed a more robust atomic theory. Dalton's theory stated that atoms were the smallest indivisible particles of matter.
* The Discovery of Electrons: In the late 19th century, J.J. Thomson conducted experiments with cathode rays, which showed that there were negatively charged particles smaller than atoms. He called these particles electrons.
* The Nuclear Model: In the early 20th century, Ernest Rutherford conducted his famous gold foil experiment, which demonstrated that atoms have a dense, positively charged nucleus at their center, surrounded by a cloud of negatively charged electrons.
* The Discovery of Protons and Neutrons: Later, Rutherford discovered protons (positively charged particles in the nucleus) and James Chadwick discovered neutrons (neutral particles in the nucleus).
These discoveries proved that atoms are not the smallest particles, but are made up of even smaller particles called subatomic particles.
It's important to note that the search for the smallest particles continues, and we now know that protons and neutrons are themselves made up of even smaller particles called quarks.
