Chapter 30 The Nucleus

Radioactivity

1. The number of protons in a nucleus is given by the atomic number.
2. The sum of the numbers of protons and neutrons in a nucleus is equal to the mass number.
3. Atoms having nuclei with the same number of protons but different numbers of neutrons are called isotopes.
4. An unstable nucleus undergoes radioactive decay, transmuting into another element.
5. Radioactivity decay produces three kinds of particles. Alpha (a) particles are helium nuclei; beta (B) particles are high speed electrons; and gamma (y) rays are high energy photons.

The Building Blocks of Matter

6. In nuclear reactions, the sum of the mass number, A, and the total charge is not changed.
7. The half- life of a radioactive isotope is the time required for half of the nuclei to decay.



8. Bombardment of nuclei by protons, neutrons, alpha particles, electrons, gamma rays, or other nuclei can produce a nuclear reaction.
9. Linear accelerators and synchrotons produce the high energy protons and electrons.
10. The Geiger counter and other particle detectors use the ionization of charged particles passing through matter.
11. In beta decay, an uncharged, massless antineutrino is emitted with the electron.
12. A positron (antimatter electron) and a neutrino are emitted by radioactive nuclei in a process called positron decay.
13. When antimatter and matter combine, all mass is converted into energy or lighter matter-antimatter particle pairs.
14. By pair production, energy is transformed into a matter-antimatter particle pair.
15. The weak interaction, or weak force, operates in beta decay. The strong force binds the nucleus together.
16. Protons and neutrons, together called nucleons, are composed of still smaller particles called quarks.
17. All matter appears to be made up of two families of particles, quarks and leptons.

Chapter 31 Nuclear Applications

Holding the Nucleus Together

1. The strong force binds the nucleus together.
2. The energy released in a nuclear reaction can be calculated by finding the mass defect, the difference in mass of the particles before and after the reaction.
3. The binding energy is the energy equivalent of the mass defect.

Using Nuclear Energy

4. Bombardment can produce radioactive isotopes not found in nature. These are called artificial radioactive nuclei and are often used in medicine.
5. In nuclear fission, the uranium nucleus is split into two smaller nuclei with the release of neutrons and energy.
6. Nuclear reactors use the energy released in fission to generate electrical energy.
7. The fusion of hydrogen nuclei into a helium nucleus releases the energy that causes stars to shine.
8. Development of a process for controlling fusion for use on Earth might provide large amounts of energy safely.