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
2 Dimensional
Model
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
Atom Anatomy
Charge
Location
PROTONS
Positive
Nucleus
NEUTRONS
Neutral
Nucleus
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