Nuclear Chemistry Unit

1. Nuclear Chemistry Unit Textbook: Ch. 19 and 20

2. Part 1: Radioactivity and Radiation

3. What is Radioactivity? • Textbook Definition • The process by which certain elements emit (give off) forms of radiation • 3 Common Types of Radiation • Alpha Particles • Beta Particles • Gamma Radiation

4. All About the Alphas (-particle) • -particles • Fast-flying • Positive Charge (++ or +2) • Essentially a Helium nucleus

5. All About the Alphas (-particle) •  particles are large, and don’t move through solid material easily • Their size gives them the most kinetic energy of the particles, so they can do significant damage • Their positive charge holds them back •  particles interact with electrons in the air and very quickly turn into harmless Helium

6. The  Team (Beta Particles) •  particles • Fast-flying • Negative Charge • Tiny mass •  particles are electrons that have been ejected (kicked out) by an atomic nucleus

7. The  Team (Beta Particles) • Smaller than alpha particles, and usually faster • Able to penetrate light materials such as paper and clothing • They can penetrate human skin, and can kill cells • Once stopped, become part of the material they are in, like any other electron

8. Gamma () Radiation • Extremely energetic form of electromagnetic radiation • No Mass • No charge • Much more energy than alpha and beta radiation

9. Gamma () Radiation • No Mass, No Charge – Pure Energy • Can penetrate most materials • Gamma rays destroy cellular molecules • Most dangerous type of radiation to humans • May be used to help fresh produce have a longer shelf life

10. Review of Radiation Penetration

11. How Radioactivity OccursNuclear Chemistry—Lecture 2 Textbook Sections 19.2 and 19.3

12. Radioactivity is a Natural Phenomenon • Radioactivity has been around longer than people • Denver gets about twice as much radiation as New Orleans. Why?

13. Biological Response to Radiation • How do cells respond to radiation? • Usually, it’s not a big deal • 90+% of your DNA isn’t important • If the DNA damage is really bad, the cell will kill itself (apoptosis—taking one for the “team”)

14. What Happens if it can’t be fixed? • If the DNA damage can’t be fixed, one of two things can happen • Apoptosis—cell kills itself • Cell Divides • If the cell divides, it produces an identical cell with the same mutation • May lead to cancer • #mutagenproblems#ohnomelanoma #aintnobodygottimeforthat

15. Radon-222 • Leading source of naturally occurring radiation • Heavier than air—accumulates in basements • Varies based on geology • Some areas of West Virginia and Pennsylvania are highly affected • Over 7000 cases of lung cancer annually due to Radon exposure

16. Strong Nuclear Force • How do protons (all + charge) hang out in the nucleus when like repels like? • Strong Nuclear Force—an attractive force between nucleons over short distances • Repulsive forces are able to act over longer distances and are also very strong forces Why do large atoms have much more neutrons than smaller atoms?

17. Strong Nuclear Force • Strong nuclear force acts over very short distances • The bigger the atom, the smaller strong nuclear force • Large atoms require more neutrons to act as a “cement” to keep the protons from repelling one another

18. Limitations of Neutrons • Neutrons aren’t stable by themselves • Can transform into a proton or electron • Lots of protons around keeps this from happening. • When there are too many neutrons, the protons can’t keep the neutrons in check (like a prison with too few guards) • When neutrons become protons, it causes the atom to eject it

19. Limitations of Strong Nuclear Force • By Strong Nuclear Force, protons are only attracted to surrounding protons and repelled by all other protons • Like a clique • As more protons are added to the nucleus, atoms become more unstable • More than 83 protons: radioactive

20. Small Atoms Can Be Radioactive • Carbon-14, an isotope, is radioactive • 8 Neutrons, 6 Protons • Not enough protons to keep the neutrons occupied, resulting in instability

21. TransmutationNuclear Chemistry Lecture 3 Textbook Section 19.4

22. Transmutation • When a radioactive nucleus emits an alpha or beta particle, the atomic nucleus changes • If the atomic number changes, the element changes • Transmutation is the changing of one element into another

23. Release of Energy • Energy is released from a transmutation reaction • Energy from gamma radiation • Kinetic Energy from alpha particle - Most of the energy released is due to the kinetic energy of the alpha particle

24.  Decay •  decay is when an element breaks down and releases an  particle • The atomic number will decrease by 2 • Atomic mass will decrease by 4

25.  Decay • As a neutron transforms to a proton, it kicks out an electron ( particle) • The atomic number will increase by 1 • The atomic mass will NOT change

27. Nuclear FissionNuclear Chemistry Lecture 4 Textbook Sections 20.1 and 20.2

28. What is Nuclear Fission? • Nuclear fission is the splitting of an atomic nucleus • When a neutron is added to U-235 it splits into… • Krypton • Barium • 3 Neutrons

29. Nuclear Chain Reactions • A nuclear chain reaction occurs when neutrons attack other radioactive atoms in succession

30. Frequency of Nuclear Chain Reactions • Nuclear chain reactions don’t occur that often in nature • U-235 is a rare isotope (1/139) of U-238, and U-235 is much more fissionable than U-238 • Remember that unstable atoms will be undergoing fission, not the stable ones which are more commonly found in nature

31. Critical Mass • Not all pieces of U-235 will result in an atomic bomb • If it’s too small, the neutrons will escape and not cause additional fission events • Critical Mass is the required size and weight of a radioactive material for a chain reaction to occur

32. Applications of Fission • Atomic Bomb • Nuclear Reactors: Nuclear Energy  Electrical Energy • 20% of the energy in the US is nuclear energy • Nuclear reactors work by boiling water to produce stream that runs a turbine • 1 kg of Uranium is more powerful than 30 freight car loads of coal

33. Nuclear Reactors • 3 Required Components • Nuclear Fuel (mostly U-238, 3% U-235) Why? • Water • Heat Transfer into a turbine • Fission plans do NOT release radioactive waste to the environment • Coal does! • Limitation: what do to the with radioactive waste products

34. Nuclear Fusionfinal Nuclear Chemistry Lecture

35. Nuclear Fusion • Definition: When small nuclei “fuse” or come together • Opposite of nuclear fission • Mass per nucleon decreases as we move from Hydrogen to Iron • Mass Lost is converted into Energy • Nuclei must be travelling at high speeds in order for fusion to occur to overcome repulsion

36. The Sun uses Nuclear Fusion • 657 million tons of Hydrogen is fused with 653 million tons of Helium every second • Loss of 4 million tons is converted into energy

37. The Thermonuclear Bomb • Temperature inside of an atomic bomb is 4-5 times greater than the sun • Hydrogen bombs, or thermonuclear bombs, are typically 1000 times more destructive than the atomic bomb dropped on Hiroshima • How? • Critical mass limits the size of a fission bomb • No such limit exists in fusion bombs

38. Fission vs. Fusion Bombs