MODELS AND THEORIES OF THE ATOM

DEMOCRITUS 400 BCE

ATOMOS THEORY

• First person to come up with the idea of atoms
• Imagined that atoms were one of two elements to make up all things
• Thought that atoms were invisible and could not be altered in any way

ARISTOTLE 380 BCE

4 ELEMENT THEORY

• Thought that there were four elements to make up the universe
• Earth, air, fire and water and any combination of two would make
• Up a sensation (i.e. Air plus water = wet or earth plus fire = hot ect.

DALTON 1800-1802

BILLIARD BALL MODEL

• His billiard ball model created the basic idea of elements.
• He said that, much like billiard balls, atoms of different elements
• Have different masses. This became the basic understanding
• For all future scientists to go off of.

THOMSON 1897

PLUM PUDDING AND CATHODE RAY

• The plum pudding model was the first model of the
• Atom to incorperate the electron. The cathode ray
• Experiment was the procedure in which he made this
• Discovery.

RUTHERFORD 1900-1903

POSITIVELY CHARGED NUCLEUS MODEL & GOLD FOIL EXPERIMENT

• Rutherford used the gold foil experiment to prove
• That the nucleus of the atom is positively charged.
• This helped explain how electrons stay with the atom.
• He was also once a student of J.J. Thomson

MILLIKAN 1923

MASS/CHARGE OF ELECTRON THEORY & OIL DROP EXPERIMENT

• His famous oil drop experiment used gravity to
• Determine the charge of an electron. This also
• Won him the nobel peace core.

CHADWICK 1925

PROTON AND NEUTRON MODEL

• He discovered neutron which created
• The model of the atom that we use today.
• He won the nobel prize for this discovery.
• He was also a student of rutherford at one point.