Models of the Atom

1904 – JJ Thomson’s Model Plum Pudding Model (or Chocolate Chip Cookie Model) His Theory: The majority of the atom is positively charged, and the electrons are embedded in the positive “core”.

Plum Pudding Model 2 Dimensional Generic Model

Cathode ray – Thomson’s experiment that was used to support the idea of electrons. The negatively charged electrons were deflected toward the positive end of the magnet.

1911 – Rutherford’s Model His Theory: He identified the nucleus and said that it was positively charged. He also said that the electrons were randomly placed around the outside of the nucleus

1913 – Bohr’s Model His Theory – He added to Rutherford’s model by including neutrons in the nucleus as well as stating that the electrons were traveling in fixed orbits around the nucleus (like planets around the sun)

1928 – Electron Cloud Model This model is the currently accepted model. EXTREMELY small, heavy nucleus that contains the protons and neutrons Electrons are very small and light and they travel around the nucleus randomly within energy levels but not in a fixed path

Bohr’s Electron Model Cloud Model

Move in space around the nucleus Atom Anatomy Charge Location PROTONS Positive Nucleus NEUTRONS Neutral ELECTRONS Negative Move in space around the nucleus

Sizes of subatomic particles Protons and neutrons are about 10,000 times bigger than electrons

SIZE OF ATOMS If you draw an line across the diameter of a penny, there are 810,000,000 atoms of Copper