History of the atomic model

Democritus (400BCEish)

Coined the term atom from atomos (greek=indivisible)

Theorised atoms were the smallest part any thing could be divided into, and that an objects characteristics depend on their atomic makeup. Atoms are infinite, aren’t created, and are eternal.

John Dalton (1803)

Solid sphere model.

Theorised atoms were indivisible, those of a given element were identical and that compounds were made of different atom types.

J. J. Thomson (1904)

Plum pudding model - electrons scattered throughout a spherical positively charged cloud.

Discovered electrons in 1897

Ernest Rutherford (1911)

Nuclear model

Fired positively charged alpha particles at a thin sheet of gold foil. Most passed straight through, however some where deflected at large angles - this is only possible if the atom is made up mostly of empty space.

Niels Bohr (1913)

Planetary model.

Modified rutherfords model to have electrons move around in set shells with fixed sizes and energies.

Erwin Schrodinger

Quantum model.

Stated electrons don’t move in set paths, but in waves. It’s impossible to find the exact location of an electron, we can only find the areas they are more likely to be in, called the orbitals. ‘probability cloud’.