Download Atomic Theories

Atomic Theories
In this unit we will learn:
• What are atoms and what are
they made of?
• What are electrons?
• How does the periodic table
help us to understand atoms?
Atomic Theories
Take an object
Atomic Theories
Take an object
Cut it in half
Atomic Theories
Take an object
Cut it in half
Do it again
Atomic Theories
Take an object
Cut it in half
Do it again
and again
Atomic Theories
Take an object
Cut it in half
Do it again
and again
and again
Atomic Theories
Take an object
Cut it in half
Do it again
and again
and again
and again
Atomic Theories
Take an object
Cut it in half
Do it again
and again
and again
and again
and again
Atomic Theories
Take an object
Cut it in half
Do it again
and again
and again
and again
and again
and again
Atomic Theories
Take an object
Cut it in half
Do it again
and again
and again
and again
and again
and again
and again
Atomic Theories
Take an object
What do
you get?
Cut it in half
Do it again
and again
and again
and again
and again
and again
and again
and again
Atomic Theories
What do
you get?
Eventually, you
might get to
something so
small that it
could not be
cut any more.
Atomic Theories
“no-cut”
a-tom
atom
Atomic Theories
Democritus
Atoms are solid,
homogeneous,
indestructible,
and indivisible.
Atomic Theories
Democritus
Changes in matter
result from changes
in the groupings of
atoms, not from
changes in the atoms
themselves.
Atomic Theories
Democritus
Why believe this?
Atomic Theories
Democritus
Why believe this?
He thought about it a
lot and it made sense
to him.
Atomic Theories
Aristotle
There are no such
things as atoms.
Atomic Theories
Aristotle
Why believe this?
Atomic Theories
Aristotle
Why believe this?
He thought about it a
lot, and it seemed
like there were too
many unanswered
questions.
Atomic Theories
John Dalton
Atomic Theories
John Dalton
• All matter is made of
atoms
Atomic Theories
John Dalton
• All matter is made of
atoms
• All atoms of an
element are identical
with each other, and
different from other
elements.
Atomic Theories
John Dalton
• Atoms cannot be
created, divided, or
destroyed
Atomic Theories
John Dalton
• Atoms cannot be
created, divided, or
destroyed
• Different atoms
combine in wholenumber ratios to
make compounds.
Atomic Theories
John Dalton
• In a chemical
reaction, atoms are
separated,
combined, or
rearranged.
Atomic Theories
Why believe this?
Atomic Theories
Why believe this?
• Experimentation
Atomic Theories
Why believe this?
• Experimentation
• Measurements of
masses and mass
ratios.
Atomic Theories
Atomic Theories
J. J. Thomson
Atomic Theories
J. J. Thomson
cathode
—
anode
+
Atomic Theories
J. J. Thomson
cathode
—
anode
+
Atomic Theories
J. J. Thomson
Atomic Theories
J. J. Thomson
Atomic Theories
J. J. Thomson
• Cathode ray tube
• Measured mass of electron
(much smaller than the smallest
atom).
Atomic Theories
Atomic Theories
Earnest Rutherford
Atomic Theories
Earnest Rutherford
Radioactive source
Atomic Theories
Earnest Rutherford
Radioactive source
in a lead box
Atomic Theories
Earnest Rutherford
Alpha particles
Radioactive source
in a lead box
Atomic Theories
Earnest Rutherford
Alpha particles
screen
Radioactive source
in a lead box
Atomic Theories
Earnest Rutherford
Alpha particles
screen
Radioactive source
in a lead box
Atomic Theories
Earnest Rutherford
Alpha particles
screen
Radioactive source
in a lead box
gold
foil
Atomic Theories
Earnest Rutherford
Alpha particles
Radioactive source
in a lead box
?
gold
foil
screen
Atomic Theories
Earnest Rutherford
Atomic Theories
Earnest Rutherford
Atomic Theories
Earnest Rutherford
Atomic Theories
Atomic Theories
Atomic Theories
Earnest Rutherford
• Shot a-particles at gold foil
• Most passed right through
• A few bounced off
• Atoms are mostly empty space
• Small, hard, dense nucleus.
Homework
Read section 4.2
Answer questions 6-9
on page 97.
In-Class Work
Problem Solving Lab
on page 96
.