Discovery of the Nucleus

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Discovery of the Nucleus

• By
• Alec Bittner
• Scott Decker
• Keith Jones
• Mona Kim
• Ben McCall

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Discovering the Nucleus
The Discovery of the Nucleus began with J.J.
Thompsons discovery of the electron.
J.J. Thompson discovered the electron in the
1890s. During this time Ernest Rutherford was a
student of his at Cambridge.
J.J. Thompson
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Plum Pudding
Thomsons theory was that atoms were made of
positive material with negatively charged
electrons all around it. This was known as the
Plum Pudding Model.
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This discovery was made while he was studying the
nature of electric discharge in a vacuum cathode
ray tube. He decided that the deflection of rays
off of magnets and electrically charged plates in
the tube was the work of something smaller than
the atom because of the large charge to mass
ratio.
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• Thomsons experiments with gamma rays, X Rays,
  and beta rays attempted to estimate the number of
  electrons in a atom while at the same time fueled
  Ernest Rutherfords desire to conduct research in
  the same field as his mentor and teacher.

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Ernest Rutherford
Ernest Rutherford was born on August 30, 1871, in
Nelson, New Zealand, the fourth child and second
son in a family of twelve children. In 1842,
Ernests father James Rutherford, a Scottish
wheelwright, emigrated to New Zealand and brought
the whole family.
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Education

• Ernest received his early education in Government
  schools. At the age of 16 he entered Nelson
  Collegiate School. In 1889 he was awarded a
  University scholarship and he began studies at
  the University of New Zealand, Wellington, where
  he entered Canterbury College.
• He graduated with an M.A. in 1893 with a
  double-class honors in Mathematics, Mathematical
  Physics, and Physical Science and he continued
  with research work at the College for a short
  time, receiving the B.Sc. degree in 1894.
• That same year, Ernest was awarded an 1851
  Exhibition Science Scholarship, enabling him to
  go to Trinity College Cambridge, as a research
  student at the Cavendish Laboratory under J.J
  Thomson.
• In 1897 he was awarded the B.A. Research Degree
  and the Coutts-Trotter Studentship of Trinity
  College. An opportunity came when the Macdonald
  Chair of Physics at McGill University, Montreal,
  became vacant, and in 1898 Ernest left for Canada
  to take up the post.

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Time brought him to Manchester University,
working with 25 year old physicist, Hans Geiger,
and a student of Hans, who helped them conduct
the experiments, Ernest Marsden.
This is a picture of Manchester University today.
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Deflection
Rutherford began experimenting with a and b
particles. He discovered that a particles
passing through matter had slight deflections.
He detected these deflections by letting them
pass through photographic film. The matter in
his experiment was a very thin sheet of 400 atom
thick gold leaf foil.
A blueprint of the Alpha Particle Deflection
detecting microscope.
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Deflection contd
He described this primary discovery almost as
incredible as if you fired a 15-inch shell at a
piece of tissue paper and it came back and hit
you.
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These are some of the actual equations used in
his calculations
?The electric field is given by this equation
This is the deflection of a particle in that
given field ?
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The Nucleus
Since the electrons carried a negative charge the
positive a particles had to be deflected by
another positive force. a spherical body too
small to be the whole atom due to the small
occurrence of deflections. Its got to be the
nucleus!
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Accomplishments of Rutherford

• Rutherford returned to England in 1907 to become
  the Professor of Physics in the University of
  Manchester, succeeding Sir Arthur Schuster. In
  1919 he accepted an invitation to succeed Sir
  Joseph Thomson as Cavendish Professor of Physics
  at Cambridge. He also became the Chairman of the
  Advisory Council, H.M. Government, Department of
  Scientific and Industrial Research Professor of
  Natural Philosophy, Royal institution, London
  and Director of the Royal Society Mond
  Laboratory, Cambridge to name a few.
• Rutherford's first researches, in New Zealand,
  dealt with the magnetic properties of iron
  exposed to high-frequency oscillations. His
  thesis was entitled Magnetization of Iron by
  High-Frequency Discharges. He was one of the
  first to design highly original experiments with
  high-frequency, alternating currents. His second
  paper, Magnetic Viscosity, was published in the
  Transactions of the New Zealand Institute (1896)
  and contains a description of a time-apparatus
  capable of measuring time intervals of a
  hundred-thousandth of a second.
• Upon his arrival to Cambridge his talents were
  quickly recognized by Professor Thomson. During
  his first spell at the Cavendish Laboratory, he
  invented a detector for electromagnetic waves an
  essential feature. An ingenious magnetizing coil
  containing tiny bundles of magnetized iron wire.
  He worked collectively with Thomson on the
  behavior of the ions observed in gases which had
  been treated with X-rays. In 1897, they also
  worked on the mobility of ions in relation to the
  strength of the electric field, and on related
  topics such as the photoelectric effect. In 1898
  he reported the existence of alpha and beta rays
  in uranium radiation and indicated some of their
  properties.

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Accomplishments Cont.

• Rutherford collaborated with Frederick Soddy in
  creating the "disintegration theory" of
  radioactivity which regards radioactive phenomena
  as atomic, not molecular, processes. The theory
  was supported by a large amount of experimental
  evidence, a number of new radioactive substances
  were discovered and their position in the series
  of transformations was fixed.
• In Manchester, Rutherford continued his research
  on the properties of the radium emanation and of
  the alpha rays. In conjunction with H. Geiger,
  Rutherford found a method of detecting a single
  alpha particle and counting the number emitted
  from the radium.
• In 1910, his investigations into the scattering
  of alpha rays and the nature of the inner
  structure of the atom which caused such
  scattering led to the Hypothesis of his concept
  of the nucleus his greatest contribution to
  physics. According to Rutherford the whole mass
  of an atom and all positive charges of an atom is
  concentrated in a minute space at the center.

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Rutherford published several books

• Radioactivity (1904)
• Radioactive Transformations (1906) his Silliman
  Lectures at Yale University.
• Radiation from Radioactive Substances,
  Co-authors James Chadwick and C.D. Ellis (1919,
  1930) - a well documented book which serves as a
  chronological list of his many papers and
  dissertations.
• The Electrical Structure of Matter (1926).
• The Artificial Transmutation of the Elements
  (1933).
• The Newer Alchemy (1937).

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Sir Rutherford

• He was awarded a Nobel Prize for Chemistry in
  1908, but his contributions benefited all
  branches of science.
• He was also knighted for his work.
• His discovery was one of the most important in
  physics.

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Beliefs Before the Nucleus
Greek Empedocle (around 492-432 BC.) divided
matter into four elements
Water Earth Fire Air
These elements are walled in by the forces of
love and hate. With absolute love, they form a
homogenous unity, whereas hate separates them.
While these two continue to enter into conflict,
the mixing of elements gives rise to all material
things. This vision of matter in some ways
pre-empted our own, with the notion of elements
bound by forces of attraction and repulsion.
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Atom The word "atom" comes from the Greek
"a-tomos" and signifies "indivisible". This
notion was invented by Leucippe of Milet in 420
BC. His disciple, Democrite of Abdere (around
460-370 BC.), explained that matter was made up
of particles in perpetual motion and endowed with
ideal qualities invisible because of their
extremely small size indivisible as their name
indicates, solid (no void inside) eternal because
they are perfect surrounded by an empty space (to
explain their movement and changes in density)
having an infinite number of shapes (to explain
the diversity observed in nature)
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Thompsons Contribution 1897, J.J. Thompson
discovered the first component part of the atom
the electron - a particle with a negative
electric charge. In 1904, he proposed an
initial model of an atom, since nicknamed
"Thompsons pudding". He imagined the atom as a
sphere full of an electrically positive substance
mixed with negative electron "like the raisins in
a cake".
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Rutherfords Role In 1912, Ernest Rutherford (New
Zealand physicist) discovered the atomic nucleus.
His new model of the atom showed that its
positive electric charge and the majority of its
mass were concentrated in an almost point sized
nucleus. The electron in an atom moves around
this nucleus like planets around the Sun, and the
attractive electric force (the negative charge of
the electron attracting the positive charge of
the nucleus) plays the role which gravity plays
for the planets which is where we get the name
"atomic planetary model".
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Differences
In contrast to the atom of the Greeks,
Rutherford's is neither indivisible (because
it's a composite structure) or solid as it
contains mostly empty space The distance of
the nucleus to the electrons is 100,000 times
greater than the diameter of the nucleus itself.
The diameter of the nucleus is approximately
10- 15 meters which is scientifically referred to
as a Fermi.
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Aftermaths of the Discovery of the Nucleus
Led to developing a model of the atom which
brought about the concept of nuclear reactions

• Nuclear reactions began new theories

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Atomic Bomb a bomb within a bomb with a bomb
outside it
Weapon of Total Destruction
Fat Man" atomic bomb was dropped on Nagasaki,
Japan killing 80,000 people
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First Nuclear Powered Submarine - nuclear power
starts to be used as a power source
Nuclear Powered Submarine
Bryan Nuclear Power Plant
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Calder Hall reactor - used natural uranium as a
source of heat
Uranium pellets used to full Nuclear Reactors
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Further Advancement

• The discovery of the nucleus led to theories of
  the electron which contributed to the formulation
  of x-rays
• Rutherford worked with Hans Geiger to begin
  atomic models
• -this interested Niels Bohr who introduced
  quantum mechanics which is the underlying
  framework of many theories of physics in the
  present day of how atoms react with each other
• (resulting in the discoveries of previously
  mentioned advancements)

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Work Cited

• http//nobelprize.org/chemistry/laureates/1908/rut
  herford-bio.html
• http//www.rutherford.org.nz/