History of the Atom

The first theory was the atomic theory, in 500 BC, which was that everything was made out of tiny particles that are separated by empty space, this idea was proposed by Democritus from ancient Greek.

Then the 1800s John Dalton said that objects were built out of spheres that make out all the elements.

After John Dalton, JJ Thomson made the "Plum pudding" model in 1897, which stated that what we would call atoms today, were not spheres but negatively charged particles, which are now named elections.
He said that 'atoms' are balls of positive charge with small amounts of negative charge.

Ernest Rutherford and his students found in 1909 that if they shot an 'Alpha' particle at a thin sheet of gold, it would pass right through if the plum pudding model was to be true, the alpha particle would have shot clean through the gold sheet.
But instead, some particles would deflect off the gold, and some would even be completely redirected the way they were coming from.

So Ernest and his students proposed the Nuclear theory, which stated that the atom was a compact nucleus which was positively charged, while the negative charge is more like a cloud around the nucleus, there was one thing that was weird about this model, as there is nothing stopping the 'cloud' of negative charge from charging into the centre of the nucleus collapsing the whole thing.

It was not until 1913 that Neils Bohr said that the electrons orbited around the nucleus in shells similar to planets around the sun the part where it orbits around the nucleus is very important.
As that is what keeps the atom from collapsing, Ernest once again found that there are small particles inside the nucleus that were giving positive charge, which we now know as Protons.

Then a person named James Chadwick provided evidence that there are neutral particles no named Newtrons along with the protons.