History of the Atomic Model

Events

Democritus

400 BC

First Scientist to create a model of an atom. Came up with the theory of atoms which is named after the Greek word Atomus which means uncuttable. He used a grain of sand to represent an atom.

John Dalton

1803

Created the atomic theory of matter. The theory states that atoms cannot be created or destroyed and that different elements can combine in whole ratios to form chemical compounds.

J Joseph Thomson

1897

Discovered the Electron. Came up with the 'Plum Pudding' model. In this model he thought that the atom was mostly positive and negativ electrons wandered around the atom.

Ernest Rutherford

1909

Created Nucleus. Said that positive matter was just in the middle. Said the atom was mostly empty space and electrons surrounded the positive nucleus.

Niels Bohr

1913

Changed orbit of electron in his model but also created energy levels in the atom, where only a certon amount of electrons could fit one energy level of the atom. This model is still used to this day

Erwin Schrödinger

1926

created his own atomic model. Thought that the only way to find the locatin and energy of an electron was to calculate the probability of being a certain distance from the nucleus.

Werner Heisenberg

1927

Said that you can't know the exact velocity and momentumof the electron at the time which means you cant know the exact location of the electron.

Louis De Broglie

1929

Believed that electrons can act like both particles and waves just like light. He said that waves were produced by electrons contained in orbit around the nucleus, set up a standing wave of certain energy, frequency and wavelength

James Chadwick

1932

Discovered the neutron.