Transcript what is matter made of? - SSFA-MsKahan

WHAT IS MATTER
MADE OF?
5 THEORIES OF MATTER
1. Fire, air, water and earth
2. Tiny, solid particles called atoms
3. Lumps of positively charged
material with negative electrons
all through it
3. A positive nucleus with negative
electrons moving around it
5. A positive nucleus with electrons orbiting around it
WHAT IS MATTER MADE OF?
• Empedocles was a Greek philosopher and scientist
• He said that matter is made of:
Why might that
make sense to
people who
knew nothing
about atoms?
SO WHAT IS MATTER MADE OF?
John Dalton, who lived in the early 1800s, said:
1. Matter is made up of tiny particles called atoms
2. Atoms can’t be created, or destroyed
3. All atoms of the same element are identical and are
different from atoms of all other elements
4. Different elements link together, in defined whole number
ratios, to make compounds
Atoms are the smallest particles
and don’t have distinct parts
Dalton’s
atom
John Dalton, who lived in
the early 1800s, said:
1. Matter is made up of tiny particles called atoms
Introduction to the Atom @ http://www.khanacademy.org/
http://www.youtube.com/watch?v=1xSQlwWGT8M&feature=fvwrel
Dalton also said:
2. Atoms cannot be created or destroyed
Dalton also said:
3. All Elements have Unique Atoms
Lithium
Gold
Sodium
Hydrogen
Uranium
Dalton also said:
2.
Dalton also said:
4. Elements combine in defined, whole number ratios
H2O – water
not H2O – water
vs.
oxygen
¾ oxygen
oxygen
hydrogen
hydrogen
½ hydrogen
hydrogen
oxygen
oxygen
oxygen
½ hydrogen
hydrogen
hydrogen
hydrogen
Dalton also said:
3.
Joseph John Thomson in 1897:
1. Discovered that atoms have negatively charged particles in them
2. Concluded that since atoms are neutral they must also contain
positive particles to balance the negatively charged particles
3. Proposed that the atom is a lump of positively charged material with
negative electrons all through it
Atoms aren’t the smallest particles
and do have distinct parts; a positive
body and electrons
your textbook’s
version
Thomson’s
atom
positive material
negative
electrons
How Thomson Found Negative Particles
Discharge Tube
Air at Very Low Pressure
1. He used a cathode ray tube like
these ones
2. The tubes contain small amounts of
gas
3. He used electricity to run a current
through the gas in the tube
4. The gas glowed
5. The glow started from the negative
end and went to the positive end
6. Opposites attract so if the glow
moved towards the positive end
that meant it must have been
negative
7. That meant some kind of negative
things from the atoms were moving
8. We now call these particles
electrons
Cathode
Green Glow
Anode
To Vacuum Pump
High
voltage
Production of Cathode Rays
Generator
Production of Cathode Rays
Green Glow Direction
Green
Glow
Starts
Here
Discharge Tube
Air at Very Low Pressure
Cathode
Green Glow
Anode
Green
Glow
Moves
to Here
To Vacuum Pump
High
voltage
Production of Cathode Rays
Generator
Green Glow Direction
Thomson’s Cathode Ray Experiment
Evidence of Electrons
Ernest Rutherford’s 1907 study of atomic structure:
1. He fired very tiny, fast, positive alpha particles at a very thin sheet of gold foil
2. He expected the alpha particles to just pass straight through the spaces
between the particles in the foil
3. Some passed straight through, some veered off on angles, and some bounced
back
4. He concluded that atoms must have a positive core that the alpha particles
were hitting
5. He named this core the nucleus and proposed that the electrons revolved
around the nucleus
Atoms aren’t the smallest particles
and do have distinct parts; a
positive nucleus and electrons
Rutherford’s
atom
positive nucleus
revolving electrons
Rutherford’s Gold Foil Experiment
Apparatus for experiment
Path of alpha (α) particles
Neils Bohr in 1912: why don’t negative electrons collapse into
the positive nucleus?
1. He thought Rutherford’s model was fundamentally correct just not complete
2. Something must be keeping the electrons from collapsing into the nucleus
3. He determined that electrons only move in defined orbitals around the nucleus
4. For electrons to move between orbitals they need specific amounts of energy
5. He called these bundles of energy quanta
Atoms have distinct parts; a
positive nucleus and electrons that
revolve around it in orbitals
Bohr-Rutherford
atom
Evolution of the Atomic Model
to be continued …
1.
Dalton’s
atom
2.
Thomson’s
atom
3.
Rutherford’s
atom
Atomic Theorists on Teacher Tube videos
http://streaming.teachertube.com/viewVideo.php?title=Atomic_Theorists&video_id=86254
4.
Bohr-Rutherford
atom