Nuclear Chemistry

1. Nuclear Chemistry ALPHA-Chemistry I-B Chapter 28

2. Wilhelm Roentgen • Wilhelm Roentgen • Discovered X-rays • Was awarded a Nobel Prize for the discovery of the mysterious rays

3. Henri Becquerel • Henri Becquerel was a part of the group that made a the early discoveries of radiation.

4. Marie Curie and her husband made the discovery of radiation. She was awarded two Nobel Prizes for her work. Marie Curie

5. The Discovery of Radiation • Henri Becquerel (1895) discovered that pitchblend (Uranium ore) would expose film. He called it radioactivity. • Marie and Pierre Curie worked long difficult hours and discovered new elements-Radium and Polonium

6. Nuclear vs. Ordinary Reactions • Ordinary chemical changes (the ones that display our indicators of chemical reactions) only involve electrons. • Nuclear changes involve the nucleus and create new atoms. • Larger atoms are from fusion • Smaller atoms are from fission

7. Radiation • Radioactivity or Radiation is the spontaneous emission of alpha, beta, or gamma rays the disintegration of the nuclei of atoms.

8. Types of Radiation • Alpha particles • A helium atom doesn’t have any electrons; positively charged. • Beta Particles • A very fast moving electron • Negatively charged • Gamma Rays • A form of energy lots of energy that moves in waves • The rays go through a lot of materials.

9. Going for the Block • Alpha particles can be blocked by a piece of paper; however, once inside the body the most immediate damage. • Beta particles can be stopped with a piece of Al foil. They do more damage over a great area of the body. • Gamma rays penetrate most things and do the most damage to DNA.

10. Radiation Protection • Distance • Time • Shielding

11. Nuclear Protective Gear

12. Alpha particles -changes the mass number by four and the atomic number by two. It’s a Helium nucleus Beta Particles -changes the atomic number by one. No change to the mass number. Neutron -no change to the mass number, but the mass changes by one. Alpha Particle Beta Particle Neutron Nuclear Equations-Know your particles and all is easy These are the main ones !!!!!!

13. The other particles • Proton • Positron

14. Five types of nuclear change • Alpha Decay • Beta Decay • Gamma Decay • Fission (spitting) • Fusion (joining)

15. Nuclear Equations • Both sides of the equation must be equal in both mass number and atomic number! • It’s just very easy algebra!

16. Examples:

17. Word Problem Example • Thorium-225 undergoes alpha decay. Write a balanced equation for the reaction.

18. A continuous flow of nuclear decay. Decay Series

19. Fission reaction • Nuclear fission is when nucleus is split into two smaller nuclei.

20. Fusion • Fusion is when two nuclei join to form a larger nucleus. The same reaction occurs in the sun!

21. A Fission Reactor • Cannot explode like a nuclear bomb. Uses a different form of uranium-238 • There is actually less pollution that goes into the air. • Nuclear weapons use uranium-235

22. Half-Life • Half life is defined as the time it takes for one half the mass of the radioactive isotope to become stable (non-radioactive) • Substances with short half-lives can cause more health hazards than isotopes with long half-lives (radiation is given off much more slowly.) • We are going to view an animation: • http://library.thinkquest.org/27948/decay.html

23. Half-Life Terms • The portion that remains radioactive is called the parent • The decayed portion is called the daughter. • The daughter is not usually radioactive, but it can be.

24. Examples • Carbon-14 has a half-life of 5700 years. How much remains of a 600 gram sample after 17,100 years? • Polonium-210 has a half-life of 138.4 days. How much remains of a 1000 gram sample after 98.86 weeks.

25. Calculating half-life • The fraction of the original amount that remains is still radioactive. • The easy way: • Determine the number of half-lives • Divide the mass by 2 until you have divided as many times as you have number of half-lives • The Formula:

26. Carbon Dating Carbon-14 and Nitrogen-14 are used to date items based on the half-life of carbon-14. We know it takes 5730 years to decay carbon-14. The amount present in the atmosphere is constant. So you just measure what’s in the artifact and work backwards.

27. Measuring Radiation-read only • Rad=Radiation Dose • Rankin=rad/hour • REM=roentgen equivalent man • 1/1000 rem = 1 mrem • LET=Linear energy transfer • A rad is the amount of energy that is released in tissue when it is irradiated. One rad=100 ergs (energy uints) deposited in one gram of tissue.

28. REM-read only • A REM measures the biological effect of radiation on the human body without having to worry about the type of radiation involved. • What’s allowed? 5-10 rems per year. It’s very rare

29. When radiation hits a cell-read only • It may pass through the cell w/o damage. • It may damage the cell, but the cell fixes the damage. • It may damage the cell; the cell reproduces the damaged form. • The cell dies-serious problems occur if too many cells are killed in a certain organ.

30. Guidelines-read only • From WWII Studies: • 650 rads Death within a few hours • 300 rads Lethal-death in 60 days • 50-250 rads Radiation sickness • Symptoms of radiation sickness • Nausea, vomiting, diarrhea, hair loss, sore throat, reduction in blood platelets, bone marrow damage • Delayed effects: Cancer, leukemia, cataracts, sterility, decreased lifespan