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CHAPTER 21 – Nuclear Chemistry
I.
Review
A. Ordinary Chemical Reactions versus Nuclear Reactions
B. Atomic Notation
Z= mass number
Z
E
A
A= atomic number
II.
Radioactivity and Writing Nuclear Equations
A. Balancing Nuclear Reactions
1. sum of mass numbers for the reactants = sum of mass numbers for the
products
2. sum of atomic numbers for the reactants = sum of atomic numbers for the
products
B. Common Types of Radioactive Decay
1. Alpha Radiation (Decay) – (Atomic mass of the atom is too large)
samarium-146 → neodymium-142 + alpha particle
2. Beta Radiation (Decay) – (n to p ratio too high)
Protactinium-234 → Uranium-234 + beta particle
Net reaction:
3. Positron emission (beta positive particle) – (p to n ratio too high)
Barium-133 → Cesium-133 + positron
Net reaction:
4. K-electron capture reactions – (p to n ratio too high)
Argon-37 + electron → Chlorine-37
Net reaction:
5. Gamma Radiation (γ) – a product of many nuclear reactions and is created
by a loss of mass.
Electron + Positron → γ
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C. Zone of Nuclear Stability and Prediction of Type of Radioactive Decay
D. Radioactive Series Reactions
Uranium-238 decays in a series of steps that contains a combination of eight
alpha and six beta steps. What is the final stable, non-radioactive product of
these decay steps?
E. Bombardment Reactions – Nuclear Transmutation
1. Bromine-80 + neutron → Bromine-81 + gamma radiation
2. Uranium-238 + carbon-12 → Californium-246 + 4 neutrons
F. Balance the following nuclear reactions and supply the missing reactant or
product
1. Nitrogen-14 + alpha particle → Oxygen-17 + __________
2. Phosphorus-30 → Sulfur-30 + __________
3. Beryllium-9 + alpha particle → neutron + ___________
III. Rate of Radioactive Decay-First Order Kinetics
A. rate = k[N]
B. ln ([N]t/[N]o) = −kt
C. t1/2 = 0.693/k
D. Gold-198 has a half life of 64.8 hours. How many grams of a 0.0100 gram
sample of this nuclide remains after 4.00 days?
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E. Isotope Dating
1. Rubidium-87 decays to Strontium-87 by beta emission. The half
life of Rubidium-87 is 5.70 x 1010 years. Analysis of a lunar rock
sample found that the ratio of Strontium-87 to Rubidium-87 is 0.0500.
Estimate the age of this lunar rock.
2. A sample of wooden artifact is found to give 7.00 counts/min/gram of
C due to 14C. A sample of new wood gives 15.3 counts/min/ gram of
C on a Geiger counter. The half life of 14C is 5720 years. Estimate the
age of this wooden artifact.
IV. Energy Changes in Nuclear Reactions
A. Einstein Equation: ΔE = Δmc2
c = speed of light = 2.9979 x 108 m/s
B. Nuclear Binding Energy – Atoms are not the sum of parts, there is always
missing mass which is called the binding energy.
Calculate the binding energy per nucleon for 6Li. The atomic mass of 6Li
is 6.01521 amu, mass of a proton is 1.00728 amu, mass of a neutron is
1.008665 amu and mass of an electron is 0.000549 amu.
Calculate mass of 6Li = 3 x (1.00728 amu) + 3 x (1.008665 amu) +
3 x (0.000549 amu) = 6.04948 amu
mass decrement = (6.04948 − 6.01521) amu = 0.03436 amu = Δm
binding energy = Δmc2 =
Calculate the binding energy of 56Fe per nucleon given that the nuclear
mass of 56Fe is 55.92068 amu.
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C. Energy from Nuclear Fission
Calculate the energy released by the nuclear reaction below. The atomic
masses are also given.
Uranium-235 + neutron → Strontium-94 + Xenon-139 + 4 neutrons
235.0439 amu 1.0087 amu 93.9154 amu
138.9179 amu 1.0087 amu
D. Energy from Nuclear Fusion
Calculate the energy released by the nuclear reaction below.
Deuterium + Tritium → Helium
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