Download 4.1 The Development of the Atomic Theory

4.1 The Development of the Atomic Theory
Greek (Democritus)
Year: 4th Century BCE
Was the atom divisible?
Universe is made up of
“indivisible” units called
atoms.
http://www.fordhamprep.org/gcurran/sho/sho/images/democri.gif
Greek
Did they do experiments? If so, what did they do?
No experiments were done.
Made up theories about how the world works.
What part of the atom was discovered or any
other information about this model?
Atoms were in motion which caused the
changes in matter that were observed
Greek
What did their model of the atom look like?
Atoms of liquid were round and smooth.
Atoms of solids were rough and prickly.
http://reichchemistry.wikispaces.com/file/view/demo._atom_model.gif/97847685/dem
o._atom_model.gif
4.1 The Development of the Atomic Theory
John Dalton
Year: Early 1800’s
Was the atom divisible?
His theory said all
matter is made up of
individual particles
that could not be
divided.
http://en.wikipedia.org/wiki/File:Dalton_John_desk.jpg
Dalton
Did they do experiments? If so what did they do?
His experiments were measuring the masses of
elements that combine when the compounds are
formed.
http://ichef.bbci.co.uk/images/ic/640xn/p01ghrbg.jpg
Dalton
What part of the atom was discovered or any other
information about this model?
Dalton’s Theory:
1. All elements are composed of atoms.
2. All atoms of the same element have the same mass, and
atoms of different elements have different masses.
3. Compounds contain atoms of more than one element.
4. In a particular compound, atoms of different elements
always combine in the same way.
Dalton
What did their model of the atom look like?
Each atom is represented as a tiny, solid
sphere with a different mass.
http://chemistryforum.yolasite.com/resources/DaltonsAtomModels%5B1%5
D.jpg
4.1 The Development of the Atomic Theory
J.J. Thomson
Year: Late 1800’s
Was the atom divisible?
Thomson’s experiments
provided evidence that
the atom is made up of
smaller particles.
http://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/J.J_Tho
mson.jpg/383px-J.J_Thomson.jpg
Thomson
Did they do experiments? If so, what id they do?
He was experimenting with electricity, called cathode
ray tubes.
1. When the current was on, the disks became
charged.
2. A glowing beam appeared
in the tube.
3. The charged plates caused
the beam to bend.
http://www.kentchemistry.com/images/links/atomic/1897_thomson2.jpg
Thomson
What part of the atom was discovered or any other
information about this mode?
1. The atom overall is neutral.
2. He hypothesized that there
was charges evenly
scattered throughout
the atom.
3. The atom was filled with a
positively charged mass
of matter.
http://withfriendship.com/images/i/40036/card-33-of-56.gif
Thomson
What did their model of the
atom look like?
“Plum-pudding model”
similar to a blueberry
muffin: the blueberries are
the electrons .
Or like chocolate chip ice
cream: the chocolate chips
are the negative electrons
in the positive ice cream
http://image.wistatutor.com/content/atoms-and-nuclei/plum-puddingmodel.jpeg
4.1 The Development of the Atomic Theory
Ernest Rutherford
Year: Early 1900’s
Was the atom divisible?
He continued with the
theory from Thomson.
http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Ernest_R
utherford_cropped.jpg/200px-Ernest_Rutherford_cropped.jpg
Rutherford
Did they do experiments? If so, what did they do?
1. He discovered that uranium emits fast moving
particles that he called alpha particles.
2. He did experiments with those particles and gold
foil.
3. He believed that the
particles would go
straight through.
4. Some of the beams
bounced back.
http://reichchemistry.wikispaces.com/file/view/Ernest_Rutherford_2.gif/44973665/Ernest_Rutherford_2.gif
Rutherford
What part of the atom was discovered or any other
information about this model?
1. All of the atom’s positive charge was concentrated in
the nucleus.
2. Alpha particles traveled
around the nucleus,
some coming very close.
http://www.daviddarling.info/images/Rutherford_atomic_model.jpg