Unit 3.1 - The Atom

Unit 3.1 - The Atom

The Evolving Model

Democritus: 460 BCE

• Greek Scientist

• Small, hard, indivisible spheres

• Coined term "Atomos"

• Means "Uncuttable"

John Dalton: 1803

• Came up with first workable model

• Indestructible, hard spheres

J.J. Thomson: 1904

• Took Chadwick's electron and proposed idea of positive particle

• Model called the "Plum Pudding Model" or the "Chocolate Chip Cookie Model"

• Negative Electrons surrounded by a "soup of positive particles"

Ernest Rutherford: 1909

• Gold Foil Experiment

• Proved the existence of the Proton

• Discovered that the Nucleus was TINY

• Electrons going around the nucleus like planets around the sun

• HUGE amount of empty space between Electrons and Nucleus

Niels Bohr: 1913

• Discovered that Electrons exist in set levels called "Electron Shells"

• Each level can only hold a specific amount of Electrons

• Each row on the Periodic Table is a new Electron Shell

Erwin Schrödinger & Werner Heisenberg: 1926

• Came up with the idea that Electrons exist in clouds

• Quantum Mechanics = math problems that can be used to predict an Electron's location at 90% accuracy