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What is Matter?
Matter is anything that has mass. All objects are made of
matter. Air, water, a brick, even you are made of matter!
States of matter
Atomic particles and isotopes
VIDEO-Clip: http://www.britannica.com/EBchecked/topic/41549/atom
Subatomic particles
Particles smaller than an atom.
They may be elementary or composite.
Electrons (elementary)
Protons (composite), made of 3 quarks
Neutrons (composite), made of 3 quarks
John DALTON
Over eighty years ago, scientists thought that the
atom was the smallest piece of matter.
Atom: the building block of matter
Solid sphere model
John DALTON (1844)
http://www.etownschools.org/Page/3502
John DALTON’s atomic theory
VIDEO CLIP: http://www.britannica.com/EBchecked/topic/41549/atom
John THOMSON discovered the electrons
1940 John Thomson
1906 Nobel Prize in Physics
Thomson at work
The Cavendish Laboratory,
Cambridge (UK)
What could these rays be?
A simple cathode ray tube.
VIDEO (3:46’) http://www.youtube.com/watch?v=4QAzu6fe8rE
Do atoms have parts?
JJ Thomson suggested that they do!
He advanced the idea that cathode rays are really
streams of very small pieces of atoms.
"We have in the cathode
rays matter in a new state."
J.J. Thomson experimenting
J.J. Thomson Talks
About the Size of the Electron
To listen to J.J. Thomson speaking on his discovery:
AUDIO: http://www.aip.org/history/electron/jjsound.htm
"Could anything at first sight seem
more impractical than a body (the
electron) which is so small that its
mass is an insignificant fraction of
the mass of an atom of hydrogen?
--which itself is so small that a crowd
of these atoms equal in number to
the population of the whole world
would be too small to have been
detected by any means then known
to science."
Recording made in 1934. From the soundtrack of the film, Atomic Physics
copyright © J. Arthur Rank Organization, Ltd., 1948.
John THOMSON’s model of the atom
Raisin cake model
J.J. Thomson theorized that electrons were surrounded by a
positively charged material, uniformly distributed.
Ernest Rutherford discovered the nucleus
1937 Ernest Rutherford
1908 Nobel Prize
Solar system model
Rutherford’s experiment
The gold-foil experiment
Alpha particle: helium nucleus (4u2+)
VIDEO: http://www.youtube.com/watch?v=Zd6_zVdMgJk
Expected results according to…..
Thomson’s model
Rutherford’s model
Rutherford’s model of the atom
Rutherford envisioned the atom as a miniature
solar system, with electrons orbiting around a
massive nucleus.
Solar system model
What is Matter?
neutrons
mesons
Quarks and gluons
Do you think that the quark is the smallest
piece of matter or do you think that there
might be
something smaller inside the quark?
You name it!
You name it!
The model of atom created by Rutherford
shouldn’t exist!
According to classical physics,
an electron in orbit around an
atomic nucleus should emit
electromagnetic radiation
(photons) continuously.
The resulting loss of energy
implies that the electron
should spiral into the
nucleus in a very short time
(atoms cannot exist!!)
Niels BOHR
1962 Niels BOHR
1922 Nobel Prize
Quantized shell model
Fixed orbits
In 1913 Bohr proposed his quantized shell model of the atom
to explain how electrons can have stable orbits around the
nucleus.
Bohr proposed that electrons
are restricted to certain fixed
(quantized) orbits.
An electron can jump between
these orbits by absorbing or
emitting a photon with the
appropriate precise wavelenght.
quantized shell model
Shell model of the atom
Bohr's idea was that each discrete orbit could only
hold a certain number of electrons. After that
orbit is full, the next level would have to be used.
This gives the atom a shell structure, in which
each shell corresponds to a Bohr orbit
VIDEO:
http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model
For working hard with me!
Electronic configuration of
different atoms
VIDEO:
http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model
Nuclear fission
VIDEO:
http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model
Atomic bonds
VIDEO:
http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model
Nuclear power
VIDEO:
http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model