31.1 Nuclear Radioactivity
A nucleus is observed to emit a ray with a frequency of What must happen to the nucleus as a consequence?
- The nucleus must gain 0.26 MeV.
- The nucleus must also emit an α particle of energy 0.26 MeV in the opposite direction.
- The nucleus must lose 0.26 MeV.
- The nucleus must also emit a β particle of energy 0.26 MeV in the opposite direction.
A uranium nucleus emits an α particle. Assuming charge is conserved, the resulting nucleus must be
31.3 Substructure of the Nucleus
A typical carbon nucleus contains 6 neutrons and 6 protons. The 6 protons are all positively charged and in very close proximity, with separations on the order of 10-15 meters, which should result in an enormous repulsive force. What prevents the nucleus from dismantling itself due to the repulsion of the electric force?
- The attractive nature of the strong nuclear force overpowers the electric force.
- The weak nuclear force barely offsets the electric force.
- Magnetic forces generated by the orbiting electrons create a stable minimum in which the nuclear charged particles reside.
- The attractive electric force of the surrounding electrons is equal in all directions and cancels out, leaving no net electric force.
31.4 Nuclear Decay and Conservation Laws
A nucleus in an excited state undergoes decay, losing 1.33 MeV when emitting a ray. In order to conserve energy in the reaction, what frequency must the ray have?
is commonly used in smoke detectors because its α decay process provides a useful tool for detecting the presence of smoke particles. When undergoes α decay, what is the resulting nucleus? If were to undergo β decay, what would be the resulting nucleus? Explain each answer.
For β decay, the nucleus releases a negative charge. In order for charge to be conserved overall, the nucleus must gain a positive charge, increasing its atomic number by 1, resulting in
A nucleus undergoes a decay process, and the resulting nucleus is . What is the value of the charge released by the original nucleus?
Explain why the overall charge of the nucleus is increased by +1 during the β decay process.
Identify the missing particle based upon conservation principles:
Are the following reactions possible? For each, explain why or why not.
31.5 Half-Life and Activity
A radioactive sample has N atoms initially. After 3 half-lives have elapsed, how many atoms remain?
When decays, the product is The half-life of this decay process is 1.78 ms. If the initial sample contains 3.4 x 1017 parent nuclei, how many are remaining after 35 ms have elapsed? What kind of decay process is this (alpha, beta, or gamma)?
31.6 Binding Energy
Binding energy is a measure of how much work must be done against nuclear forces in order to disassemble a nucleus into its constituent parts. For example, the amount of energy in order to disassemble into 2 protons and 2 neutrons requires 28.3 MeV of work to be done on the nuclear particles. Describe the force that makes it so difficult to pull a nucleus apart. Would it be accurate to say that the electric force plays a role in the forces within a nucleus? Explain why or why not.