Journal #22
October 6, 2015
How did the
model of this
dinosaur get to
the detail that
you see in the
picture?
Atomic Models
460 BC – Democritus coined the term ATOM
•Greek word “A TOMOS” meaning
uncuttable.
Early 1800s– Dalton confirms ATOM particles
•English chemist, John Dalton performed
experiments with various chemicals that
showed that matter, indeed, consists of
elementary particles.
1897 – Thomson discovers electrons
•In 1897, the English physicist J.J. Thomson
discovered the electron and estimated its
mass to be much smaller than the positive
matter of an atom.
•He determined that electrons are negatively
charged and the rest of matter was
positively charged.
1897 – Thomson discovers electrons
•Cathode Ray
Group Activity
•Draw your FIRST atomic model using ONLY
the knowledge discussed thus far in this
period.
•Label with #1.
1911 – Rutherford’s Gold Foil Experiment
•Determined that the atom is mostly empty
space with a condensed center.
•He named it the “Nucleus”.
1911 – Rutherford’s Gold Foil Experiment
Group Activity
•Draw your SECOND atomic model using
ONLY the knowledge discussed thus far in
this period.
•Label with #2.
1912 – Bohr makes 2 rules that describe the
way atoms operate.
•RULE 1: Electrons can orbit only at certain
allowed distances from the nucleus.
•RULE 2: Atoms radiate energy when an
electron jumps from a higher-energy orbit
to a lower-energy orbit. Also, an atom
absorbs energy when an electron gets
boosted from a low-energy orbit to a highenergy orbit.
1912 – Bohr Finding.
Group Activity
•Draw your THIRD atomic model using ONLY
the knowledge discussed thus far in this
period.
•Label with #3.
1927 – "Heisenberg uncertainty principle."
• No experiment can measure both the position
and momentum of a quantum particle
simultaneously.
• Sub-atomic particles behave as both particles
and waves (similar to light).
• There are certain regions (orbitals) around a
nucleus where an electron is more likely to be
found. We cannot know their exact position.
1927 – "Heisenberg uncertainty principle."
Group Activity
•Draw your FOURTH atomic model using
ONLY the knowledge discussed thus far in
this period.
•Label with #4.
Gallery Walk
With your group, list the following:
1) Does the model match the information
available at the time of discovery.
2) What are the limitations for each
group’s models.
Now let’s see the original models.
Thomson’s Plum Pudding Model
Rutherford’s Model
Bohr Model
Exit Slip
1) Explain why Bohr modeled the atom
with distinct rings around the atom.
2) Explain what the orbitals represent in
the quantum atomic model.