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SPS3 Students will distinguish the characteristics and components of radioactivity.
Warm-up: review:
strong force vs. electric forceunstable nucleinuclear decaynuclear decay problems3 types of radiationFission vs. fusionHalf life problems
Calculating Half-Life Problems
An isotope of cesium (cesium-137) has a half-life of 30 years. If 1.0 gram of cesium-137 disintegrates overa period of 90 years, how many grams of cesium-137 would remain?
Time Mass
0 1.030 .5060 .2590 .125
2. Actinium-226 has a half-life of 29 hours. If 100 mg of actinium-226 disintegrates over a period of 58 hours, how many mg of actinium-226will remain?
masstime
0 100 mg29 hours 50 mg58 hours __ mg
•Nuclear fission is the process of splitting a nucleusInto several smaller nuclei.
•Only large nuclei, such as the nuclei of uranium andplutonium atoms can undergo nuclear fission.
•The products of a fission reaction usually include several individual neutrons in addition to the smallernuclei.
•The total mass of the products is slightly less than the mass of the original nucleus. Some of the original mass is converted to energy!!
Chain Reactions: requires more neutrons eachsuccessive generation.
Critical mass – is the amount of materialrequired so that each fission reaction produces approximately one more fissionreaction. If less than the critical massIs present, a chain reaction will not occur.
Nuclear fusion occurs when two nucleiwith low masses are combined to formone nucleus of larger mass.
Fusion fuses atomic nuclei togetherand fission splits nuclei apart.
Please copy fission/fusionreactions from the board.How can you tell the difference?
For nuclear fusion to occur, positively chargednuclei must get close to each other.
But remember they have an electric repulsiveForce.
If nuclei are moving fast, they can have enough kinetic energy to overcome the repulsive electrical force between them.
Only at temperatures of millions of degrees Celsius are nuclei moving so fast that they canget enough for fusion to occur.
Most of the energy given off by the sun is caused from the fusion of four hydrogen nuclei into one heliumnucleus.
One day, all of the hydrogen nucleiwill be converted into helium and fusionwill stop.
