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Agenda 3/3/10• Pick up your lab• Take out homework - Isotopes WS• Did you take the moodle quizzes?• Notes on balancing decay reactions• Practice balancing decay reations WS• 6th period – review last week’s quiz
Learning Goal: Students will be able to write balanced decay reactions for alpha and beta decay.
Isotope Review1. Determine the number of protons and neutrons
in each of the following isotopes.
H31
Neon-22
2. Determine the name and symbol for an isotope whose atoms contain 3 protons and 4 neutrons.
Isotope Review1. Determine the number of protons and neutrons
in each of the following isotopes.
H31
Neon-22
2. Determine the name and symbol for an isotope whose atoms contain 3 protons and 4 neutrons.
1 Proton2 Neutrons
10 Protons12 Neutrons
Lithium-7 Li 73
Decay ReactionsWhen a radioactive isotope decays…- matter is conserved.- total # of particles in the nucleus is conserved.- total (neutral) charge of atom is conserved.
Decay ReactionsWe can use those conservation ideas to predict decay products. For example, when Uranium-238 decays by alpha decay…
U23892 → + ______
alpha particle
daughter nucleus
Decay ReactionsWe can use those conservation ideas to predict decay products. For example, when Uranium-238 decays by alpha decay…
U23892 → He4
2 + ___alpha
particledaughter nucleus
Decay ReactionsWe can use those conservation ideas to predict decay products. For example, when Uranium-238 decays by alpha decay…
U23892 → He4
2 +alpha
particledaughter nucleus
Th23490
Another ExampleWrite the decay reaction formula for the alpha decay of Bismuth-211.
Bi21183 → + ______
alpha particle
daughter nucleus
Another ExampleWrite the decay reaction formula for the alpha decay of Bismuth-211.
→alpha
particledaughter nucleus
He42 + Tl207
81Bi21183
One More Alpha-Decay ExampleA certain radioactive isotope decays by alpha decay, producing Silicon-31 as the daughter nucleus. What was the original isotope?
Si3114→ +___
alpha particle
___original nucleus
One More Alpha-Decay ExampleA certain radioactive isotope decays by alpha decay, producing Silicon-31 as the daughter nucleus. What was the original isotope?
Si3114→ +He4
2S3516
Beta DecayBeta decay still obeys the same general conservation rules as alpha decay, but it works a little differently because of what beta particles are. A beta particle is basically just…
an electron emitted from the nucleus!
Beta DecaySo what would the symbol for a beta particle look like, in a decay reaction formula?
e-1
Remember, this bottom number is the # of protons, which could also be
thought of as the charge of the particle.
0This top number counts how
many total protons and neutrons are present in this particle.
Beta Decay ExampleNow that you know the symbol, predicting decay products should be easy enough. What are the products when Carbon-14 decays by beta decay?
C146 → + ______
betaparticle
daughter nucleus
Now that you know the symbol, predicting decay products should be easy enough. What are the products when Carbon-14 decays by beta decay?
C146 → + ___
betaparticle
daughter nucleus
e0-1
Beta Decay Example
Now that you know the symbol, predicting decay products should be easy enough. What are the products when Carbon-14 decays by beta decay?
C146 → +
betaparticle
daughter nucleus
e0-1 N14
7
Beta Decay Example
What’s occurring in the nucleus during beta decay, for the total #of particles in the nucleus to remain constant, but for proton # to increase?
C146 → +
One of the neutrons is ‘breaking’ into a proton and an electron.
e0-1 N14
7
Beta Decay Example
One More Beta-Decay ExampleWrite the decay reaction formula for the beta decay of Phosphorous-32.
P3215 → + ______
betaparticle
daughter nucleus
Write the decay reaction formula for the beta decay of Phosphorous-32.
P3215 →
betaparticle
daughter nucleus
+ S3216e0
-1
One More Beta-Decay Example
Decay Reaction PracticeDetermine the daughter nucleus produced when each of the following radioactive isotopes decay in the manner stated.
1. (beta)
2. (alpha)
Ca4520
Pu23494
3. (alpha)
4. (beta)
Po21084
Na2411
Decay Reaction Answers
1.
2.
Sc4521
U23092
3.
4.
Pb20682
Mg2412
