The History of the The History of the Atomic ModelAtomic Model

In other words, the old guys In other words, the old guys who came up with the atom.who came up with the atom.

DemocritusDemocritus460 BC - 370 BC460 BC - 370 BC

A Greek philosopher A Greek philosopher proposed that all proposed that all matter was matter was composed of composed of indivisible hard balls indivisible hard balls called atoms (Greek called atoms (Greek for uncuttable). for uncuttable).

Unfortunately he Unfortunately he was unpopular and was unpopular and ignored.ignored.

John DaltonJohn Dalton18031803

Billiard Ball Model : Billiard Ball Model : viewed the atom as viewed the atom as a small solid a small solid sphere.sphere.

But he got the ball But he got the ball rolling again to rolling again to study the atom.study the atom.

Joseph John Thomson Joseph John Thomson 18971897

Plumb Pudding Model: Plumb Pudding Model: Proposed that the Proposed that the atom was a sphere of atom was a sphere of positive energy with positive energy with negative particles negative particles imbedded throughout. imbedded throughout.

He was awarded the He was awarded the Nobel Prize in physics Nobel Prize in physics in 1906 for in 1906 for discovering the discovering the electron. electron.

Ernest Rutherford Ernest Rutherford 19101910

Solar System Solar System Model: discovered Model: discovered that the atom is that the atom is mostly empty mostly empty space with a dense space with a dense positively charged positively charged nucleus nucleus surrounded by surrounded by negative electrons. negative electrons.

How Did He KnowHow Did He Know He beamed particles He beamed particles

through gold foil and through gold foil and detected them as detected them as flashes of light .flashes of light .

Most of the alpha Most of the alpha particles went particles went straight through the straight through the foil, but some were foil, but some were deflected by the foil deflected by the foil and hit a spot on a and hit a spot on a screen placed off to screen placed off to one side. one side.

Neils Bohr Neils Bohr 19131913

Proposed that Proposed that electrons traveled electrons traveled in circular orbits in circular orbits and that only and that only certain orbits were certain orbits were allowed.  allowed. 

Erwin Schrodinger Erwin Schrodinger 19261926

Electron Cloud Model: Electron Cloud Model: Using math Erwin Using math Erwin found that an atom found that an atom consists of a dense consists of a dense nucleus composed of nucleus composed of protons and neutrons protons and neutrons surrounded by surrounded by electrons that exist in electrons that exist in different clouds at the different clouds at the various energy levels. various energy levels.