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AP Chem
Nuclear Chemistry Assignment
What you need to know:
1. How to recognize types of nuclear decay, ie alpha, beta, gamma, electron capture,
and positron emission.
2. How the nucleus changes during each type of decay.
3. The relative penetrating ability of each type of radiation.
4. How to calculate the mass defect for a nuclear process
5. How to calculate the energy per nucleus and energy per mole of a nuclear process.
6. How to calculate the amount of isotope left after any amount of time if you have a
calculator.
7. How to calculate the amount of an isotope left after an integral number of half
lives without a calculator.
8. Write nuclear equations. How to predict the relative stability of isotopes using
mass number and atomic mass.
9. How to predict which type of decay an isotope will undergo using mass number
and atomic mass.
10. The identity of the two most stable nuclides and why they are the most stable.
Overview:
Protons and neutrons are found in the nucleus of atoms. They are called nucleons
and are made of quarks. The strong nuclear force opposes the electromagnetic force by
which protons repel each other. Certain ratios of protons and neutrons are stable, others
are less stable. Ratios that won’t hold together don’t hold together. Ratios that hold
together but decay at a noticeable rate are radioactive. Ratios that don’t decay at a
noticeable rate are stable. The most stable situation is an even number of protons and an
even number of neutrons. The least stable situation is when both numbers are odd. There
are only four (or five) stable odd/odd nuclei.
Nuclides with a mass number over 200 usually undergo alpha decay. They emit a
particle consisting of two protons and two neutrons. Nuclides with too many neutrons
undergo beta decay and those with too many protons undergo positron emission or
electron capture.
Radioactive decay is a first order process. These equations let us solve for the
amount of nuclide left at time T: ln2/k = half-life; lnA = -kT + lnA0
Problem Set:
Chapter 21: 20, 21, 22, 29-41 odd, 43-49 odd, 53-61 odd, 75, 77, 97
1. Name the three particles that make up atoms. For each give the symbol, charge, and
mass number.
2. Write equations for alpha decay, beta decay, gamma decay, electron capture, and
positron emission.
3. Name the three main types of radiation given off during nuclear decay, arrange them
from highest penetration to lowest and draw a picture showing how they interact with
electric fields.
4. Define the band of stability and draw a picture of it.
5. Predict the type(s) of decay that nuclei with the following issues will undergo:
A. Too many protons
B. Too many neutrons
C. Heavy nuclide
6. How long does it take for 80% of a sample of 14C to decay? The half-life is 5730
years.
7. What changes in a nuclide result from the loss of each of the following?
a.
b.
c.
d.
e.
f.
An alpha particle.
A gamma ray.
An electron.
A positron.
A neutron.
A proton.
8. Write a balanced equation for each of the following nuclear reactions.
a. Bismuth-212 decays to polonium-212.
b. Uranium-230 undergoes alpha decay.
c. Beryllium-8 and a positron are produced by the decay of an unstable
nucleus.
d. Fusion of a deuterium nucleus (2H) and a tritium nucleus (3H) giving a
helium nucleus and a neutron.
e. A fission reaction producing Sb-133, Nb-99, and 4 neutrons following
capture of a neutron by a U-235 nucleus.
f. The production of 14C from 14N by neutron bombardment.
g. The production of 239U from 238U by 21H bombardment.
9. Why is electron capture accompanied by emission of an X-ray?
10. How does nuclear fission differ from nuclear fusion? Why are both of these
processes exothermic?
11. The iodine that enters the body is stored in the thyroid gland from which it is
released to control growth and metabolism. The thyroid can be imaged if iodine-131 is
injected into the body. In larger doses I-131 is also used as a means of treating cancer of
the thyroid. I-131 has a half-life of 8.70 d and decays by e- emission. Emission of a
gamma ray accompanies the beta decay.
a. Write an equation for the decay. (It is customary to omit gamma rays in
nuclear equations that involve production of new nuclei or other particles.)
b. Is the beta particle or the gamma ray used in the imaging process?
c. How long will it take for 95.0% of a dose of I-131 to decay.
12. Calculate the density of the 2412Mg nucleus in g cm-3, assuming that it has the typical
nuclear diameter of 1 x 10-13 cm and is spherical in shape (V = 4/3 r3).
13. What is the age of mummified primate skin that contains 8.25% of the original
quantity of 14C?