Radioactive and Nuclear Chemistry
Explain the concept of half-life with respect to radioactive nuclides. What rate law is characteristic of radioactivity?
A half-life is the time it takes for one-half of the parent nuclides in a radioactive sample to decay to the daughter nuclides. The first-order integrated rate law is characteristic of radioactivity.
What is a beta particle? What happens to the mass number and atomic number of a nuclide that emits a beta particle?
A neutron is turned into a proton and emits an electron. The atomic number increases A beta particle is a medium-energy particle released during beta decay. It is equivalent to an electron. The mass number does not change, but the atomic number increases by one during beta decay.
Describe the process of electron capture. What happens to the mass number and atomic number of a nuclide that undergoes electron capture?
A proton is added to an electron and turns into a neutron. Atomic number decreases by 1 Electron capture is the form of radioactive decay that occurs when a nucleus assimilates an electron from an inner orbital. The mass number does not change, but the atomic number decreases by one during electron capture.
What is a positron? What happens to the mass number and atomic number of a nuclide that emits a positron?
A proton is turned into a neutron and emits a positron. The atomic number decreases by 1 A positron is the particle released in positron emission. It is equal in mass to an electron, but opposite in charge. The mass number does not change, but the atomic number decreases by one during positron emission.
What is an alpha particle? What happens to the mass number and atomic number of a nuclide that emits an alpha particle?
Alpha particles have the same symbol as the helium nucleus. When elements emit an alpha particle, the number of protons in its nucleus will decrease by a factor of two while the mass number decreases by a factor of four. This means that the element will be changed to a different element.
What are magic numbers? How are they important in determining the stability of a nuclide?
Magic numbers represent certain number of nucleons that confer unique stability. Since these magic numbers are even in number, this in part accounts for the abundance of stable nuclides with even numbers of nucleons. Moreover, nucleons also have a tendency to pair together. This tendency and the resulting stability of paired nucleons also contribute to the abundance of stable nuclides with even numbers of nucleons.
Describe fission. Include the concepts of chain reaction and critical mass in your description. How and by whom was fission discovered? Explain how fission can be used to generate electricity.
Nuclear fission is the splitting of the nucleus of an atom, resulting in a tremendous release of energy
The products of a nuclear reaction usually have a different mass than the reactants. Why?
The products of a nuclear reaction usually have a different mass than the reactants becase some matter has been converted into enrgy. Einstein's famous equation, E=mc^2 show the relationship between the amount of matter that is lost and the amount of energy formed.
Explain why the ratio of neutrons to protons (N>Z) is important in determining nuclear stability. How can you use the N>Z ratio of a nuclide to predict the kind of radioactive decay that it might undergo?
or lighter elements, the N/Z ratio of stable isotopes is around one due to the equal numbers of neutrons and protons. When Z is 20, the N/Z ratio starts to get bigger (~1.5). Once Z reaches 83, the stable nuclei ceases to exist.
What is a gamma ray? What happens to the mass number and atomic number of a nuclide that emits a gamma ray?
Gamma rays are high energy photons and have a short wavelength. A gamma ray doesn't have a charge or a mass. When a gamma ray photon is emitted, it doesn't change the mass number or atomic number of the element.
