History of the atom.

who discovered the atom

Democritus- apparently the first to describe invisible “atoms” as the basis of all matter and that they were indestructable.

John Dalton

He proposed the Atom theory of mater- atoms were tiny, solid, indivisible particles

plum pudding model

A ball of of positive charge embedded with negative electrons.

Who made the plum pudding model?

J.J. Thomson in 1904

alpha particle scattering experiment

Rutherford first alpha particles at a thin sheet of gold foil (so particles wont get absorbed). Most cut straight through, others deflected slightly and some deflected straight back.

Rutherford’s conclusion

The atom has a ball of positive charge in the center which is the nucleus, most of the atom is empty space and electrons is separate to the nucleus.

What did Bohr do?

Discovered that electrons orbit the nucleus at set distances, and they were in shells.

Who discovered neutrons and when?

James Chadwick -1932