Test Prep for AP® Courses
14.2 Substructure of the Nucleus
A typical carbon nucleus contains six neutrons and six protons. The six 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.
14.3 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.
14.4 Half-Life and Activity
A radioactive sample has N atoms initially. After three 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?
14.5 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 two protons and two 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.