1. Unstable nuclei emit radiation. Radioactive elements have unstable nuclei. Elements 84 and higher are all radioactive.
2. Radioisotopes are radioactive isotopes of atoms that also have stable isotopes. Ex. C-14 (carbon with a mass of 14) is a radioisotope of carbon.
3. Transmutation is when a radioisotope changes into a new element because radiation was released. Two types natural and artificial.
4. Natural transmutation occurs without the help of another particle (reactant).
5. Artificial transmutation occurs with the help of another particle.
6. Three types of radiation. Table O
A. Alpha particles = He nucleus with a mass of 4 and a +2 charge
B. Beta particles = electron with a mass of zero and a –1 charge
C. Gamma rays are pure energy with no mass and no charge
7. Alpha particles are attracted to the negative poles
8. Beta particles are attracted to the positive poles
9. Gamma rays pass straight through.
10. During alpha decay the mass number will decrease by 4 and the atomic number decreases by 2
11. During beta decay the mass number will not change and the atomic number increases by 1
12. During gamma decay mass and atomic number don’t change.
13. During positron emission the mass doesn’t change and the atomic number decreases by 1.
14. Nuclear equations must balance by mass and charge (atomic #)
15. Fusion is the fusing of two light (He or H) nuclei to form a heavier nucleus. A tremendous amount of NRG is released. A fission reaction is necessary to provide enough nrg for fusion to take place because there is tremendous repulsion of two positive nuclei that must be overcome.
16. Fission is the splitting of a heavy nucleus using 3 neutrons. U-235 and Pu-239 are fissionable materials. Not as much nrg as fusion is released. Waste products are hazardous because they emit radiation.
17. Fission creates energy from mass. E=mc2
18. Half-life is the time it takes for half of a sample to decay. Half-life never changes. Table N gives half-life information.
19. You should be able to calculate fraction remaining, mass of original sample, and age using half-life.
20. Uses of radioisotopes:
a. C-14 dating of organic material and to trace pathways of organic chemical reactions.
b. U-238 dating of rocks
c. I-131 is used to detect thyroid problems
d. Co-60 is used to kill cancer cells
e. Tc-99 is used as a tracer to detect cancer
21. Radioisotopes used for medicine have short half-lives and are eliminated quickly from the body.
22. Radiation is harmful to humans (especially gamma rays) because they can cause genetic mutations in sex cells (sperm and eggs). Radiation can also cause normal cells to become cancerous.
Examples of Nuclear reactions:
1. Alpha decay: 226 Ra à 222 Rn + 4He
88 86 2
2. Beta decay: Pb à Bi + e
3. Positron emission: K à Ar + e
4. Artificial Transmutation: Co + n à Co
5. Nuclear Fission: n + U à Ba + Kr + 3n + energy
6. Nuclear Fusion: H + H à He