1. Isotopes Variants of a chemical element
All isotopes of a given element have the same # of protons
Differ in the number of neutrons
Hydrogen
Deuterium
Tritium

2. Isotopes General Form: AXZ 1H1 2H1 3H1
Chemical symbol for the element: X
Atomic # (# of Protons): Z
Protons + Neutrons: A
Hydrogen
Deuterium
Tritium
1H1
2H1
3H1

3. Radioactive Decay Beta Decay Alpha Decay Electron Emission (β-)
238U92 => 234Th90 + 4He2
Beta Decay
Electron Emission (β-)
3H1 => 3He2 + 0e-1
234Th90 => 234Pa91 + 0e-1
Electron Capture
40K e-1 => 40Ar18 + hv
Postitron Emission (β+)
40K19 => 40Ar18 + 0e+1

4. Trinity Test
Trinity Test Video

5. 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
Alpha Particle
Thin Foil 7Li
11B

6. Early History of the Bomb
Fermi repeats bombarding experiment with neutrons and finds:
Uranium produces several radioactive by products. α β γ
Neutron N
Uranium β γ

7. Uranium-235 Fission
1N U92  236U92 144Ba Kr36 + 3N + ENERGY
Protons + Neutrons  = 236
Protons  = 92
Protons + Neutrons  = 236
Protons  = 92

8. 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??

9. Early History of the Bomb
1939—Leo Szilard confirms that neutrons are produced and an explosive chain reaction is possible.

10. 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.

11. Fission of Uranium
Mass of a Neutron = u

12. Fission of Uranium Mass of a Neutron = 1.008 u
Mass of 235U = u

13. Fission of Uranium Mass of a Neutron = 1.008 u
Mass of 235U = u
Mass of 144Ba56 = u

14. Fission of Uranium Mass of a Neutron = 1.008 u
Mass of 235U = u
Mass of 144Ba56 = u
Mass of 89Kr36 = u

15. Fission of Uranium Mass of a Neutron = 1.008 u
Mass of 235U = u
Mass of 144Ba56 = u
Mass of 89Kr36 = u
1N U92  236U92 144Ba Kr36 + 3N + ENERGY

16. Fission of Uranium Mass of a Neutron = 1.008 u
Mass of 235U = u
Mass of 144Ba56 = u
Mass of 89Kr36 = u
1N U92  236U92 144Ba Kr36 + 3N + ENERGY =

17. Fission of Uranium Mass of a Neutron = 1.008 u
Mass of 235U = u
Mass of 144Ba56 = u
Mass of 89Kr36 = u
1N U92  236U92 144Ba Kr36 + 3N + ENERGY =
(1.008) =

18. Fission of Uranium Mass of a Neutron = 1.008 u
Mass of 235U = u
Mass of 144Ba56 = u
Mass of 89Kr36 = u
1N U92  236U92 144Ba Kr36 + 3N + ENERGY =
(1.008) =
Δ M = u

19. Fission of Uranium
Δ M = u
1 u = 1.66 x kg

20. Fission of Uranium
Δ M = u
1 u = 1.66 x kg
E = mc2

21. 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

22. 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 = * Joules

23. 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 = * Joules
Note: 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 = x Joule

24. 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 = * Joules
Note: 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 = x Joule
2.775 x J x
1 eV
1.73 x 108 eV
173. x 106 eV = =
1.602 x J

25. 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 = * Joules
Note: 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 = x Joule
2.775 x J x
1 eV
1.73 x 108 eV
173. x 106 eV = =
1.602 x J =
173 MeV

26. So What’s the Big Deal??
If * Joules of energy are released in one fission
What if 1 Kg of Uranium 235 fissions?
How much energy is released?

27. So What’s the Big Deal??
If * Joules of energy are released in one fission
What if 1 Kg of Uranium 235 fissions?
How much energy is released?
1 mole 235U92 = g
1 Kg = 1000 g

28. So What’s the Big Deal??
If * Joules of energy are released in one fission
What if 1 Kg of Uranium 235 fissions?
How much energy is released?
1 mole 235U92 = g
1 Kg = 1000 g
1000 g 235U92 x 1 mole 235U92 =
4.25 Moles 235U92
g 235U92

29. The Big Deal 4.25 Moles 235U92 x 6.022 x 1023 atoms =
2.56*1024 Atoms 235U92
mole

30. The Big Deal 4.25 Moles 235U92 x 6.022 x 1023 atoms =
2.56*1024 Atoms 235U92
mole
If 1 Kg of 235U92 fissions, we get:
2.775 X Joule x
2.56*1024 Atoms 235U92 =
7.10* 1013 Joules
Atom

31. The Big Deal 4.25 Moles 235U92 x 6.022 x 1023 atoms =
2.56*1024 Atoms 235U92
mole
If 1 Kg of 235U92 fissions, we get:
2.775 X Joule x
2.56*1024 Atoms 235U92 =
7.10* 1013 Joules
Atom
As a comparison: 1 TON of TNT
4.184* 109 Joules

32. The Big Deal 17,000 Tons of TNT 4.25 Moles 235U92 x 6.022 x 1023 atoms=
2.56*1024 Atoms 235U92
mole
If 1 Kg of 235U92 fissions, we get:
2.775 X Joule x
2.56*1024 Atoms 235U92 =
7.10* 1013 Joules
Atom
As a comparison: 1 TON of TNT
4.184* 109 Joules
7.10* 1013 Joules =
1.7* 104 Tons of TNT
1 Kg of 235U92
4.184* 109 Joules
17,000 Tons of TNT

33. Fission Videos
Nuclear Fission
Chain Reaction

34. Fission Cross Sections

35. The Problem Fission occurs in about 10-8 seconds
80 Generations pass in 0.8 microseconds
It takes less than a millionth of a second to fission a kg of 235U

36. The Solution Equivalent to 20,000 Tons of TNT
Use a gun to shoot the slug in
Little Boy Gun Type Weapon
Equivalent to 20,000 Tons of TNT

37. Fat Man Bomb

38. Fat Man Bomb

40. Homework Given the Equation:
1N U92  236U92 144Ba Kr36 + 3N + ENERGY
What percentage of the mass is converted to energy?