Download 4 - University of Miami

Chemistry 101 H
Discovering The Secrets of
The Nucleus
Chapter 4 - Discovering The
Secrets of The Nucleus
This presentation was created by
Professor Carl H. Snyder
Chemistry Department
University of Miami
Coral Gables, FL 33124
[email protected]
Copyright 2004 by Carl H. Snyder,
University of Miami. All rights
reserved.
The Bomb
The story of the
atomic bomb
The chemistry of the
atomic bomb
1896 - 1945
Madame Curie’s Discovery
The spot is caused by a form of radiation - radioactivity -- that comes fom the
uranium atoms themselves and
penetrates through the film’s wrapper.
Becquerel’s
Discovery
A bit of a uranium
compound placed on a
sealed envelope
containing some
unexposed film . . .
. . . produced a spot
on the film.
Becquerel, 1896
Radioactivity
The spontaneous emission of radiant
energy and/or high-energy particles
from the nucleus of an atom.
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Rutherford’s Discoveries
The atom contains a central core, a
positively charged nucleus.
Radioactivity is emitted from this nucleus.
Radioactivity consists of more than one
kind of radiation.
Becquerel, Curie, Rutherford
Becquerel, Nobel
Prize 1903
Curie (with her
daughter), Nobel Prize
1903 (and 1911)
Rutherford, Nobel
Prize 1908
1899
Penetrating Power
Alpha-, Beta-, and Gamma-rays
Alpha-particles: highenergy helium nuclei
Beta-particles: highenergy electrons
Alpha-rays are stopped most easily.
Beta-rays are intermediate in penetrating power.
Gamma- rays penetrate matter readily.
Atomic Number, Mass Number
Mass number appears
to upper left of symbol
Gamma-rays: highenergy
electromagnetic
radiation
Characteristics of
Radioactivity
Atomic number
appears to lower left of
symbol
Charge appears to
upper right of symbol
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Radioactive Decay of Tritium
Beta-decay of tritium produces He-3
Radioactive Decay of U-238
Radioactive Decay of C-14
Beta-emission from C-14 produces N-14
A Chain of Radioactive Decay:
U-238
U-238 -- alphadecay to Th-234.
Th-234 -- betadecay to Pa-234.
The chain continues
through a series of
radioisotopes.
And ends at the
stable isotope, Pb206.
Alpha-decay of U-238 produces Th-234
Rutherford’s Transmutation of
Nitrogen
Subatomic Particles
Quarks - Fundamental particles that
compose larger subatomic particles
such as protons and neutrons
Gluon - A subatomic particle that holds
quarks together in their clusters.
Transmutation is the process of converting
one element into another element.
Positron - A subatomic particle that
carries a charge of 1+ but is otherwise
identical to an electron.
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Friedman, Taylor, Kendall
Chadwick’s Discovery of the
Neutron
Jerome I. Friedman
James Chadwick
Shared Noble Prize
with Richard E. Taylor
and Henry W. Kendall
Experimental
observation of quarks
Experimental
demonstration of the
neutron, 1932
Nobel Prize, 1935
1990
Hahn and Meitner
Nuclear Fission
The splitting of a nucleus into two or more
large fragments.
Fission also releases considerable
energy.
Otto Hahn discovered (1938) and Lise Meitner
named nuclear fission.
Hahn, Nobel Prize, 1944
U-235 Fission
U-235 Fission Observed by
Hahn
Two of many modes of U-235 fission.
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Cascading Effect in Chain
Reaction
Critical Mass
Chain Reaction
The Leaders of the Manhattan
Project
General Leslie Groves
(right) headed the
entire project.
Dr. Robert
Oppenheimer (left) led
the technical team that
designed and built the
bombs.
Gaseous Diffusion
UF6 molecules containing U-235 have a lower mass
than UF6 molecules containing U-238.
The 235UF6 molecules move faster than the 238UF6
molecules.
The 235UF6 accumulate faster in the chamber on the
right.
How The U-235 Bomb Works
Conventional explosive fires a sub-critical plug
of U-235
into a hollow, sub-critical cylinder of U-235
creating a critical mass of U-235.
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How The Pu-239 Bomb Works
Fat Man and Little Boy
Fat Man: Plutonium
Little Boy: Uranium
Conventional explosive surrounding a hollow,
sub-critical sphere of Pu-239
implodes the hollow Pu-239 sphere into
a solid, critical mass of Pu-239.
The shapes of the bombs
reflect the mechanism of
detonation.
Einstein
Mass Defect
Albert Einstein
E = mc2
Mass and energy are
equivalent
Nobel Prize, 1921 (for
the unrelated
photoelectric effect)
Binding Energy
Conversion of Mass to Energy
In U-235 fission, a little less than 0.1 % of the
total mass of the reactants is converted into
energy:
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The Energy of A 100-Watt
Light Bulb
The Energy of The Sun
The Sun’s energy comes from the fusion of four
atoms of protium to form one atom of helium.
Nuclear Fusion
The Energy of The Hyrdogen
Bomb
The energy of the hydrogen bomb comes from
the fusion of a deuterium atom with a tritium
atom to form a helium atom.
End - Chapter 4
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