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Isotopes
• Variants of a chemical element– All isotopes of a given element have the same # of
protons– Differ in the number of neutrons
TritiumHydrogen Deuterium
Isotopes
• General Form: AXZ
– Chemical symbol for the element: X– Atomic # (# of Protons): Z – Protons + Neutrons: A
TritiumHydrogen Deuterium
1H13H1
2H1
Radioactive Decay• Alpha Decay • 238U92 => 234Th90 + 4He2
• Beta Decay– Electron Emission (β-)– 3H1 => 3He2 + 0e-1
– 234Th90 => 234Pa91 + 0e-1
– Electron Capture– 40K19 + 0e-1 => 40Ar18 + hv– Postitron Emission (β+)– 40K19 => 40Ar18 + 0e+1
Early History of the Bomb
• 1931—Crockroft & Walton split the atom• 1932—Chadwick discovers the neutron (Nobel
Prize 1953• 1934—Joliot & Curies bombard a target to
produce new elements using α particles
α
Thin Foil 7Li 11BAlpha Particle
Early History of the Bomb
• Fermi repeats bombarding experiment with neutrons and finds:– Uranium produces several radioactive by products.
Neutron
Uranium
β
γ
N
β
γ
α
Uranium-235 Fission
• 1N0 + 235U92 236U92 144Ba56 + 89Kr36 + 3N + ENERGY
• Protons + Neutrons 1 + 235 = 236
• Protons 0 + 92 = 92
• Protons + Neutrons 144 + 89 + 3 = 236
• Protons 56 + 36 = 92
Early History of the Bomb
• 1938—Hahn & Stassmann prove that Fermi observed fission and published 12/22/1938.– Fermi Wins Nobel Prize.
• 1939—Frisch and Meitner describe fission and the potential for large amounts of energy to be released.– The Question? Are neutrons liberated in the
process??
Early History of the Bomb
• 1939—Leo Szilard confirms that neutrons are produced and an explosive chain reaction is possible.
Early History of the Bomb
• 1939—April 22. Letter in Nature by Joliot confirmed that excess neutrons are produced and a chain reaction is confirmed.
• World War II begins.
Fission of Uranium
• Mass of a Neutron = 1.008 u
Fission of Uranium
• Mass of a Neutron = 1.008 u• Mass of 235U = 235.044 u
Fission of Uranium
• Mass of a Neutron = 1.008 u• Mass of 235U = 235.044 u• Mass of 144Ba56 = 143.923 u
Fission of Uranium
• Mass of a Neutron = 1.008 u• Mass of 235U = 235.044 u• Mass of 144Ba56 = 143.923 u
• Mass of 89Kr36 = 88.918 u
Fission of Uranium
• Mass of a Neutron = 1.008 u• Mass of 235U = 235.044 u• Mass of 144Ba56 = 143.923 u
• Mass of 89Kr36 = 88.918 u • 1N0 + 235U92 236U92 144Ba56 + 89Kr36 + 3N + ENERGY
Fission of Uranium
• Mass of a Neutron = 1.008 u• Mass of 235U = 235.044 u• Mass of 144Ba56 = 143.923 u
• Mass of 89Kr36 = 88.918 u • 1N0 + 235U92 236U92 144Ba56 + 89Kr36 + 3N + ENERGY• 1.008 + 235.044 = 236.052
Fission of Uranium
• Mass of a Neutron = 1.008 u• Mass of 235U = 235.044 u• Mass of 144Ba56 = 143.923 u
• Mass of 89Kr36 = 88.918 u • 1N0 + 235U92 236U92 144Ba56 + 89Kr36 + 3N + ENERGY• 1.008 + 235.044 = 236.052• 143.923 + 88.918 + 3(1.008) = 235.865
Fission of Uranium
• Mass of a Neutron = 1.008 u• Mass of 235U = 235.044 u• Mass of 144Ba56 = 143.923 u
• Mass of 89Kr36 = 88.918 u • 1N0 + 235U92 236U92 144Ba56 + 89Kr36 + 3N + ENERGY• 1.008 + 235.044 = 236.052• 143.923 + 88.918 + 3(1.008) = 235.865• Δ M = 0.187 u
Fission of Uranium
• Δ M = 0.187 u• 1 u = 1.66 x 10-27 kg
Fission of Uranium
• Δ M = 0.187 u• 1 u = 1.66 x 10-27 kg• E = mc2
Fission of Uranium
• Δ M = 0.187 u• 1 u = 1.66 x 10-27 kg• E = mc2
• E =(1.66 x 10-27) (0.187kg) x (2.99 x 108)2
Fission of Uranium
• Δ M = 0.187 u• 1 u = 1.66 x 10-27 kg• E = mc2
• E =(1.66 x 10-27) (0.187kg) x (2.99 x 108)2
• E = 2.775 * 10-11 Joules
Fission of Uranium
• Δ M = 0.187 u• 1 u = 1.66 x 10-27 kg• E = mc2
• E =(1.66 x 10-27) (0.187kg) x (2.99 x 108)2
• E = 2.775 * 10-11 JoulesNote: A unit we like to use is the electron volt (eV). This is the energy an electron will gain as it moves across an electric potential difference of one volt. 1eV = 1.602 x 10-19 Joule
Fission of Uranium
• Δ M = 0.187 u• 1 u = 1.66 x 10-27 kg• E = mc2
• E =(1.66 x 10-27) (0.187kg) x (2.99 x 108)2
• E = 2.775 * 10-11 JoulesNote: A unit we like to use is the electron volt (eV). This is the energy an electron will gain as it moves across an electric potential difference of one volt. 1eV = 1.602 x 10-19 Joule
2.775 x 10-11 J x
1.602 x 10-19 J
1 eV = 1.73 x 108 eV = 173. x 106 eV
Fission of Uranium
• Δ M = 0.187 u• 1 u = 1.66 x 10-27 kg• E = mc2
• E =(1.66 x 10-27) (0.187kg) x (2.99 x 108)2
• E = 2.775 * 10-11 JoulesNote: A unit we like to use is the electron volt (eV). This is the energy an electron will gain as it moves across an electric potential difference of one volt. 1eV = 1.602 x 10-19 Joule
2.775 x 10-11 J x 1 eV = 1.73 x 108 eV =
=
173. x 106 eV
173 MeV1.602 x 10-19 J
So What’s the Big Deal??
• If 2.775 * 10-11 Joules of energy are released in one fission– What if 1 Kg of Uranium 235 fissions?– How much energy is released?
So What’s the Big Deal??
• If 2.775 * 10-11 Joules of energy are released in one fission– What if 1 Kg of Uranium 235 fissions?– How much energy is released?1 mole 235U92 = 235.044g
1 Kg = 1000 g
So What’s the Big Deal??
• If 2.775 * 10-11 Joules of energy are released in one fission– What if 1 Kg of Uranium 235 fissions?– How much energy is released?1 mole 235U92 = 235.044g
1 Kg = 1000 g1000 g 235U92 x 1 mole 235U92
235.044 g 235U92
= 4.25 Moles 235U92
The Big Deal4.25 Moles 235U92 6.022 x 1023 atoms
molex
= 2.56*1024 Atoms 235U92
The Big Deal4.25 Moles 235U92 6.022 x 1023 atoms
molex
= 2.56*1024 Atoms 235U92
If 1 Kg of 235U92 fissions, we get:
2.775 X 10-11 Joule Atom
x 2.56*1024 Atoms 235U92 = 7.10* 1013 Joules
The Big Deal4.25 Moles 235U92 6.022 x 1023 atoms
molex
= 2.56*1024 Atoms 235U92
If 1 Kg of 235U92 fissions, we get:
2.775 X 10-11 Joule Atom
x 2.56*1024 Atoms 235U92 = 7.10* 1013 Joules
As a comparison: 1 TON of TNT 4.184* 109 Joules
The Big Deal4.25 Moles 235U92 6.022 x 1023 atoms
molex
= 2.56*1024 Atoms 235U92
If 1 Kg of 235U92 fissions, we get:
2.775 X 10-11 Joule Atom
x 2.56*1024 Atoms 235U92 = 7.10* 1013 Joules
As a comparison: 1 TON of TNT 4.184* 109 Joules
1 Kg of 235U92 7.10* 1013 Joules
4.184* 109 Joules1.7* 104 Tons of TNT=
17,000 Tons of TNT
Fission Videos
•Nuclear Fission
•Chain Reaction
Fission Cross Sections
The Problem
Fission occurs in about 10-8 seconds80 Generations pass in 0.8 microsecondsIt takes less than a millionth of a second to fission a kg of 235U
The Solution
Equivalent to 20,000 Tons of TNT
Use a gun to shoot the slug in
Little Boy Gun Type Weapon
Fat Man Bomb
Fat Man Bomb
Homework
• Given the Equation:• 1N0 + 235U92 236U92 144Ba56 + 89Kr36 + 3N + ENERGY
– What percentage of the mass is converted to energy?
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