1. NUCLEAR CHEMISTRY

2. FYI: Historical Perspective
Henri Becquerel
Discovers natural radioactivity

3. FYI: Historical Perspective
Marie Sklodowska, Polish chemist marries Pierre Curie, French physicist
Marie died from leukemia caused by her exposure to radiation
Pierre was killed while crossing the street when he was hit by a vegetable wagon.

4. FYI: Historical Perspective
Ernest Rutherford
1899 – Discovers alpha, beta and gamma radiation

5. Nuclear Reactions Involve changes in the composition of nuclei
Accompanied by the release of tremendous amounts of energy

6. Nuclear Fission
The splitting of a heavy nucleus into lighter nuclei

7. Nuclear Fusion
The combination of light nuclei to produce a heavier nucleus

8. The neutron-to-proton ratio determines the stability of the nucleus
For low atomic #’s:
Equal #’s of protons and neutrons
Above atomic #20:
More neutrons than protons

9. Nuclei whose neutron-to-proton ratio is unstable undergo radioactive decay by emitting 1 or more particles and/or electromagnetic rays:

10. Nuclei whose neutron-to-proton ratio is unstable undergo radioactive decay by emitting 1 or more particles and/or electromagnetic rays:
Type/
symbol
Identity
Mass (amu)
Charge
Penetration
Alpha
Beta
Gamma
Proton
Neutron
helium nucleus
4.0026 2+
low
electron 1-
low-med
high energy radiation
high
proton, H nucleus
1.0073 1+
low-med
neutron
1.0087
very high

11. Comparing penetrating ability…

12. Alpha Particle Decay
Example 1: Radium-226 transmutates by alpha decay. Write the nuclear equation that represents this process. or

13. + +
Beta Particle Decay
Example 2: Write the nuclear equation for the beta-decay of boron-12. or

14. Gamma Radiation
Example 3: Write the nuclear equation representing gamma radiation given off by the unstable radionuclide cobalt-60.

15. Nuclear Fission & Fusion

16. FISSION: a heavy nucleus splits into 2 lighter nuclei
some elements undergo fission spontaneously
some elements can be induced to undergo fission when bombarded with other particles (e.g. neutrons)

17. FUSION: 2 nuclei combine to form a heavier nucleus
the sun is a tremendous fusion reaction; the major fusion reaction in the sun is thought to be:
both fission & fusion release large amounts of energy (fusion more than fission)

18. The Atomic Bomb (FISSION)
when the nucleus of U-235 splits, 2 isotopes are formed, plus neutrons are emitted
these neutrons collide with other U-235 atoms, causing them to undergo fission; they release neutrons, and so on…
The result - CHAIN REACTION!!

19. FISSION

20. The Atomic Bomb (FISSION)

21. The Atomic Bomb (FISSION)

22. One type of bomb… Little Boy: U-235 (Hiroshima)
Fat Man: Pu-239 (Nagasaki)
subcritical mass of U-235
TNT (dynamite)
subcritical mass of U-235

23. Nuclear Reactors (controlled FISSION)

24. Nuclear Reactors (FISSION)
use subcritical masses of fissionable material
CORE: contains fuel pins made of U-235; interspersed among the pins are control rods
control rods: absorb neutrons
pull rods out of core: fission increases
push rods back into the core: fission decreases
Safety feature: if power is lost, rods will automatically fall into the core and shut the reaction down.

25. Nuclear Reactors (FISSION)
“The energy produced by breaking down the atom is a very poor kind of thing. Anyone who expects a source of power from the transformation of these atoms is talking moonshine.”
Ernest Rutherford

26. Nuclear Reactors (FISSION)

27. Nuclear Power Plants

28. Nuclear Power Plants

29. Nuclear Power Plants

30. TO GENERATE ELECTRICITY:
Fission heats up water in vessel and heat is carried away.
This heat is used to heat up water in a second system, which turns into steam.
Steam turns turbine of a generator.
Generator makes electricity.

31. PROS OF NUCLEAR ENERGY:
no air pollution
enormous amt. of energy released
alternative to using our rapidly decreasing fossil fuels

32. CONS OF NUCLEAR ENERGY
containers for waste products may erode or break
thermal pollution (heated water returned to rivers, etc.)
potential theft of fuel (Pu-239) for use in weapons

33. Controlled Nuclear FUSION
PROS:
A very abundant supply of energy world wide.
Environmentally clean
No creation of weapon materials
No chance of runaway reactions leading to accidents
CONS:
It doesn’t work; at least not yet…

34. Nuclear Fusion
"Every time you look up at the sky, every one of those points of light is a reminder that fusion power is extractable from hydrogen and other light elements, and it is an everyday reality throughout the Milky Way Galaxy."
Carl Sagan, Spitzer Lecture, October 1991

35. Nuclear Fusion Obstacles… HOT – plasma at least 100 million C
High density plasma
Containment of plasma
Confinement time

36. Rates of Decay & Half Life
Radionuclides have different stabilities and decay at different rates.

37. HALF-LIFE= the amount of time required for half of the original sample to decay

38. HALF-LIFE= the amount of time required for half of the original sample to decay
Daughter
Parent

39. Example: Cobalt-60 decays with the emission of beta particles and gamma rays, with a half-life of 5 years. How much of a 3.42 g of cobalt-60 remains after 15 years?

40. Uses of Radionuclides
Radiocarbon dating: the ages of specimens of organic origin can be estimated by measuring the amount of cabon-14 in a sample.

41. Uses of Radionuclides
***NOTE: Objects older than 50,000 years have too little activity to be dated accurately using carbon dating; instead the following methods are used:
Potassium-40 decays to argon-40: half-life = 1.3 x 109 years
Uranium-238 decays to lead-206: half-life = 4.51 x 109 years

42. Example: A sample of uranium ore is found to contain 4
Example: A sample of uranium ore is found to contain 4.64 mg of uranium-238 and 1.22 mg of lead Estimate the age of the ore.