Atomic History

Democritus

• all atoms are small hard particles
• made of  single materials formed into shapes and sizes

ATOMOS

John Dalton

• all matter is made of atoms
• atoms of an element have identical mass and properties
• compounds are formed by two or more different atoms
• a chemical reaction is a rearrangement of atoms

Dalton's Atomic Model

J. J. Thomson discovered that rays could be deflected by an electric field, and that cathode rays were made of what he called "corpulces". these are now called electrons

plum pudding model

Ernest Rutherford discovered that toms have a nucleus and also that radioactivity decays after a long period of time.

Rutherford created a new model of the atom in which all positive charges are inside a small,massive nucleus about ten-thousand times smaller than the whole atom.

Niels Bohr's theory states that electrons travel in circular orbits around the nucleus.

Untitled Slide

Schrodinger and Heisenburg are responsible for the modern theory, the Electron Cloud.

An Electron Cloud locates the area around the atomic nucleus where electrons will probably be.