Evolution of the Atom

Democritus

• Used Philosophy
• Believed atoms were indivisible and indestructible
• Believed everything was made up of atoms

John Dalton

• Came up with Atomic Theory
• Pictured atoms as tiny, indestructible particles 
• Also with no internal structure
• Said atoms can't be made or destroyed

J.J. Thomson

• Discovered the electron
• This lead to his "plum pudding" model
• Pictured electrons embedded in a sphere
• The sphere was of positive electrical charge

Ernest Rutherford

• Found that atom has a nucleus
• Nucleus is small, dense, and positively charged
• Said electrons move around nucleus

Neils Bohr

• Said the electron orbits around the nucleus
• Electron can gain or lose energy by changing orbit
• Moves in circular orbits

Erwin Schrodinger

• Developed mathematical equations 
• Equations described motions of the electrons
• His lead to the electron cloud model

James Chadwick

• Confirmed the existence of neurtrons
• Neutrons have no charge
• Atomic nuclei contain nuertrons and protons