5: Nuclear Chemistry
- Page ID
- 402255
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- 5.1: Nuclear Reactions
- Nuclear reactions are very different from chemical reactions. In chemical reactions, atoms become more stable by participating in a transfer of electrons or by sharing electrons with other atoms. In nuclear reactions, it is the nucleus of the atom that gains stability by undergoing a change of some kind. The energies that are released in nuclear reactions are many orders of magnitude greater than the energies involved in chemical reactions.
- 5.2: The Discovery and Nature of Radioactivity
- In 1896, Henri Becquerel found that a uranium compound placed near a photographic plate made an image on the plate and reasoned that the compound was emitting some kind of radiation. Further investigations showed that the radiation was a combination of particles and electromagnetic rays, with its ultimate source as the atomic nucleus. These emanations were ultimately called, collectively, radioactivity. The major types of radioactivity include alpha particles, beta particles, and gamma rays.
- 5.3: Stable and Unstable Isotopes
- In nuclear reactions, it is the nucleus of the atom that gains stability by undergoing a change of some kind. A radioisotope is an isotope of an element that is unstable and undergoes radioactive decay. The energies that are released in nuclear reactions are many orders of magnitude greater than the energies involved in chemical reactions. Unlike chemical reactions, nuclear reactions are not noticeably affected by changes in environmental conditions, such as temperature or pressure.
- 5.4: Nuclear Decay
- Unstable nuclei spontaneously emit radiation in the form of particles and energy. This generally changes the number of protons and/or neutrons in the nucleus, resulting in a more stable nuclide. One type of a nuclear reaction is radioactive decay, a reaction in which a nucleus spontaneously disintegrates into a slightly lighter nucleus, accompanied by the emission of particles, energy, or both.
- 5.5: Radioactive Half-Life
- Natural radioactive processes are characterized by a half-life, the time it takes for half of the material to decay radioactively. The amount of material left over after a certain number of half-lives can be easily calculated.
- 5.6: Ionizing Radiation
- The effects of radiation on matter are determined primarily by the energy of the radiation. Nonionizing radiation is relatively low in energy; when it collides with an atom in a molecule or an ion, most or all of its energy can be absorbed without causing a structural or a chemical change. In contrast, ionizing radiation is higher in energy, and some of its energy can be transferred to one or more atoms with which it collides as it passes through matter.
- 5.7: Measuring Radiation
- We previously used mass to indicate the amount of radioactive substance present. However, this is only one of several units used to express amounts of radiation. Some units describe the number of radioactive events occurring per unit time, while others express the amount of a person's exposure to radiation.