Title: Discovery of the Nucleus
1Discovery of the Nucleus
- By
- Alec Bittner
- Scott Decker
- Keith Jones
- Mona Kim
- Ben McCall
2Discovering 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
3Plum 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.
4This 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.
5- 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.
6Ernest 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.
7Education
- 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.
8Time 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.
9Deflection
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.
10Deflection 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.
11These 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 ?
12The 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!
13Accomplishments 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.
14Accomplishments 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.
15Rutherford 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).
16Sir 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.
17Beliefs 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.
18Atom 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)
19Thompsons 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".
20Rutherfords 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".
21Differences
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.
22Aftermaths 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
23Atomic 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
24First Nuclear Powered Submarine - nuclear power
starts to be used as a power source
Nuclear Powered Submarine
Bryan Nuclear Power Plant
25Calder Hall reactor - used natural uranium as a
source of heat
Uranium pellets used to full Nuclear Reactors
26Further 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)
27Work Cited
- http//nobelprize.org/chemistry/laureates/1908/rut
herford-bio.html - http//www.rutherford.org.nz/