Nuclear Chemistry
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Dr. Melinda Oliver
Bishop State Community College
A short review of the nucleus
Let's focus on the nucleus
Mass number and atomic number
A little practice
Radioactivity-unstable atomic nuclei
Alpha decay
Beta decay
Gamma rays
The band of stability shows the effect of the ratio of neutrons (N) over protons (P) N/P
Practice Problems
2. Write balanced nuclear equations for the following transformations: (a) bismuth-213 undergoes alpha decay, (b) nitrogen-13 undergoes electron capture, (c) technicium-98 undergoes electron capture, (d) gold-188 decays by positron capture.
3. What particle is produced during the following decay processes: (a) sodium-24 decays to magnesium-24, (b) mercury-188 decays to gold-188, (c) iodine-122 decays to xenon-122, (d) plutonium-242 decays to uranium-238.
4. A radioactive decay series that begins with thorium-232 ends with the formation of the stable nuclide lead-208. How many alpha-particle emissions and how many beta-particle emissions are involved in the sequence of radioactive decays?
5. Each of the following nuceli undergoes either beta decay or positron emission. Predict the type of emission for each: (a) tritium, 3 1H; (b) 8938Sr, (c) iodine-120, (d) silver-102.
6. In 1930 the American physicist Ernest Lawrence designed the first cyclotron in Berkeley, California. In 1937 Lawrence bombarded a molybdenum target with deuterium ions, producing for the first time an element not found in nature. What was this element? Starting with molybdenum-96 as your reactant, write a nuclear equation to represent this process.
7. Complete and balance the following nuclear equations by supplying the missing particle:
(a) N-14 + 4 alpha → ? + H-1
(b) K-40 + beta (orbital electron) → ?
(c) ? + alpha → H-1 + S-30i
(d) Fe-58 + 2neutrons → ? + Co-60
(e) U-235 + neutron → ? + X-135e +2neutrons
One of the four fundamental forces in nature is the Strong Nuclear Force
The mass defect-the most famous science equation!
You have learned that in chemical reactions, mass is conserved. For the most part, this is correct. There are very minimal mass differences that using Einstein's famous equation would translate into small amounts of energy. That is what the equation is about-the direct relation between mass and energy. There is a great book on this equation. The history behind every piece (even the equal sign). For those interested:
So, in typical chemical reactions some of the mass (about 9.9 x 10^-9 g for the combustion of one mole of methane) is lost but this is pretty minimal. However, plug it into the equation and you do get some energy out of it.
The mass lost in nuclear reactions is much larger. For a typical alpha emission:
the mass lost (product mass-reactant mass) is -0.0046 g. Plug this into the equation (convert mass into kg so energy comes out in joules) and you end up with -4.11 x 10^11 J, a pretty significant amount of energy.
Practice Problems
2. The isotope nickel-62 has the largest binding energy per nucelon of any isotope. Calculate this value from the atomic mass of nickel-62 (61.928345) and compare it with the value given for iron-56 (1.41 x 10^-12 J/nucleon).
Half-Life
Fission
Fusion
Practice Problems
2. A wooden artifact from a Chinese temple has a carbon-14 activity of 38.0 counts per minute as compared with an activity of 58.2 counts per minute for a standard of zero age. From the half-life for carbon-14 decay, 5715 yr, determine the age of the artifact.
3. The half-life for the process 238U --> 206Pb is 4.5 x 109 yrs. A mineral sample contains 75.0 mg of 238U and 18.0 mg of 206Pb. What is the age of the mineral?
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Dr. Melinda Oliver
Bishop State Community College
Email: moliver@bishop.edu
Location: Mobile, AL, United States
Phone: (251)405-4504