nuclear chemistry
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Radiation
In this part of the unit, we will focus on the nucleus! It’s very small (10-13 cm)
It’s very dense (1.6 ×14 g/cm3)
A lot of energy holds it together!(millions of times more than involved in chemical
reactions!)
Many nuclei are RADIOACTIVE!
They spontaneously decompose or DECAY (break apart) forming a different nucleus & producing
one or more particles
3 Main Types of Decay Particles
Alpha (α) particles Slow moving
nucleus of a helium atom.
Not very dangerous, can be stopped by▪ Skin▪ A piece of paper
3 Main Types of Decay Particles
Beta ( β) Particles Faster moving
electrons Are harmful Can be stopped by
wood or metal sheets
3 Main Types of Decay Particles Gamma (γ)
Particles High-energy
photon of light Very dangerous Partially stopped by
6 inches of lead or 6 feet of concrete
Half-Life (t1/2)
Time it takes for half of a radioactive material to decay away.
Example: You have 100.g of Ra-221. It’s half-life is
30 seconds.▪ What does that mean?
▪ How much Ra-221 would be left after 90 seconds?
More Half-Life Problems
The half-life of I-131 is 8.02 days. How much I-131 is left after 32.08 days? You originally have 600.g.
The half-life of Pu-239 is 24,360 years. Starting with 1000.g, how much would be left after 146,160 years?
Would it ever completely decay away?
Fission
Process of splitting a heavy nucleus into two more stable nuclei with smaller mass numbers
Releases a lot of energy
Fission
Chain reaction When you have a
lot of a radioactive substance and the fission of one nucleus gives off particles that hit other nuclei that give off more particles that hit more nuclei. . .
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