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• Unstable nuclei emit radiation to attain more stable atomic configurations in a process called radioactive decay.
• During radioactive decay, unstable atoms lose energy by emitting one of several types of radiation.
• Elements with atomic # higher than 83 are all radioactive.
Types of Radiation1. Alpha particles
• Given off when a nucleus releases 2 protons and 2 neutrons
• Same as a helium nucleus
• Largest and slowest form of radiation
• Least penetrating
• Can be stopped by a sheet of paper
2. Beta particles
• Neutron decays into a proton and electron
• Electron (beta particle) is emitted at very high speed
• Proton stays in nucleus
• Increases the atomic number by one – new element is formed
• Does not affect the mass number
• Much faster than alpha particles
• Can be stopped by a thin metal foil or wood
3. Gamma rays
• Most penetrating and potentially dangerous
• Highest energy and frequency
• No mass, no charge
• Travel at speed of light
• Lead and concrete used to stop rays
Half-Life
Amount of time it takes for half of a sample of radioactive isotope to decay
Carbon-14 is used in radioactive datingHalf-life of carbon is 5730 years.
Calculating Amount of Remaining Isotope
• Iron-59 is used in medicine to diagnose blood circulation disorders.
• The half-life of iron-59 is 44.5 days.
• How much of a 2.000-mg sample will remain after 133.5 days?
Honors Half-Life Problems Answers
1. 0.125 mg
2. 2016
3. 25 mg
4. 1 mg
5. 0.625 mg
6. 6.0 years
7. 75 min
8. 31,250 atoms
9. 0.0625 g; 102.4 g
10. 20 minutes
11. 3.875 x 1018 atoms,
12. 120 s
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Uses of Nuclear Energy & Radiation
Radioactive datinguses isotopes of known half-life to determine age of rocks, fossils, etc.
Cancer therapy (radiation treatment)gamma radiation kills cancerous AND healthy cells
Imaging
inject radioactive isotopes into the body
“see” the inner workings of the body by following radioactive isotopes
Smoke detectors
atomic bombs = uncontrolled fission reactions
nuclear reactors = controlled fission reactions
heat used to generate steam & electrical power
Nuclear Fusion
Also called thermonuclear reactions
Combining of two or more nuclei to form one nucleus of larger mass
Requires extremely high temperatures or strong magnetic field
Occurs in the sun & H-bombs