1. Physical Science – Ms. Oster - 2015
Radiation Notes
Physical Science – Ms. Oster

2. Monday 12/7 Please grab a new bellringer sheet
Don’t forget to be completing and turning in any late work- every point counts!
Work through the exam review sheet in order to make a “cheat sheet” for the midterm!
Today’s Bellringer: What do you think of when you hear the term radiation?

3. Radiation
Radiation is dangerous energy or particles given off by radioactive materials.

4. Sources of Radiation
Radiation is released in large amounts by atomic bombs and nuclear power plants

5. Effects of Radiation
Burns the Skin
Cancer
Birth Defects in Children

6. Chernobyl
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7. What Causes Radioactivity?
Atoms are radioactive when the nucleus has too many protons “packed together”
The positive charges push against each other and make the atom unstable
This instability causes the nucleus to break apart (decay) by throwing off particles / energy

9. Rates of Decay Radioisotope: Radioactive isotope of an element
Nuclear decay is the deterioration of a radioisotope
The types of decay are alpha, beta, and gamma
Half-life: The amount of time required for half of a sample of a radioisotope to decay /watch?v=tzM6aK5QbSU

10. Rates of Decay
After 1 half-life, half of the atoms of a radioactive sample have decayed and the other half remains radioactive
After 2 half-lives another half of the material decays and ¼ of the original amount remains

11. Rates of Decay Calculations:
Half lives can vary from fractions of a second to billions of years
Nuclear reaction rates are constant, whereas chemical reaction rates can vary
Calculations:
Half lives elapsed =
Total time of decay
Half Life

12. Half Life Practice
Half lives elapsed =
Total time of decay
Half Life
You have one gram of iridium-182, which decays to osmium-182. The half life is 15 minutes.
How much iridium will remain after 45 minutes?
Half lives elapsed =
45 minutes
15 minutes

13. Rates of Decay Half lives elapsed= 3
That means we cut the sample in half 3 times:
½ x ½ x ½ = 1/8
If we have 1/8 of one gram then we have
1/8 x 1 gram= .125 grams

14. Practice Problems
An isotope of cesium-137 has a half life of 30 years. If 5.0 mg of cesium-137 decays over a period of 90 years, how many grams of the sample remain?
Half lives elapsed =
Total time of decay
Half Life
3 half lives have elapsed
Half lives elapsed =
90 years
30 years
3 half lives= ½ x ½ x ½ or 1/8 of the original sample
1/8 x 5.0 mg= .625 mg cesium-137

15. Assignment
5 half life problems