Unstable Nuclei and Radioactive Decay

You now have a good understanding of the basic structure of matter and how matter interacts and changes through processes called chemical reachons. With the informahon you have just learned about the atom s nuclear nature, you are ready to learn about a very different type of reaction—the nuclear reaction. This sechon introduces you to some of the changes that can take place in a nucleus you will revisit and further explore this topic in Chapter 25 when you study nuclear chemistry. 

As you learned in the previous section, the number of protons in the nucleus determines the idenhty of an atom. Thus, because there are no changes in the nuclei during a chemical reaction, the identities of the atoms do not change. There are, however, reactions that do involve an atom of one element changing into an atom of another element. These reactions, which involve a change in an atom s nucleus, are called nuclear reactions. 

Would you enjoy the challenge of removing contaminated materials If so, consider a career as a radiation protection technician. 

Radiation protection technicians use radiation measuring instruments to iocate and assess the risk posed by contaminated materiais. Then they decontaminate the area with high-pressure cieaning equipment and remove the radioactive materiais. The work often requires the technicians to wear protective suits. The phys-icaiiy demanding work is care-fuiiy pianned and carried out, with an emphasis on safety. 

Because alpha, beta, and gamma radiation possess different amounts of electrical charge, they are affected differently by an electric field. Gamma rays, which carry no charge, are not deflected by the electric field. 

I Explain the relationship between unstable nuclei and radioactive decay. I Characterize alpha, beta, and gamma radiation in terms of mass and charge. 

Unstable atoms emit radiation to gain stability. 

Real-World Reading Link Try dropping a rock from the height of your waist. The rock goes from a higher energy state at your waist to a lower energy state on the floor. A similar process happens with nuclei in an unstable state. 

Recall from Chapter 3 that a chemical reaction is the change of one or more substances into new substances and involves only an atoms electrons. Although atoms might be rearranged, their identity remains the same. Another type of reaction, called a nuclear reaction, can change an element into a new element. 

Nuclear reactions In the late 1890s, scientists noticed that some substances spontaneously emitted radiation in a process they named radioactivity. The rays and particles emitted by the radioactive material were called radiation. Scientists discovered that radioactive atoms undergo changes that can alter their identities. A reaction that involves a change in an atoms nucleus is called a nudear reaction. The discovery of these nuclear reactions was a major breakthrough, as no chemical reaction had ever resulted in the formation of new kinds of atoms. 

we know that some nuclei are unstable and gain stability by emitting radiation. This process is called radioactive decay. 

The second common type of radiation is beta radiation, which consists of high-energy electrons called beta particles (P-particles). 

It is important to realize that each of these beta particles is emitted by the atom s nucleus, thereby increasing its atomic number (and charge) by H-. 

The third type of radiation is gamma radiation (y-radiation), which is high-energy electromagnetic radiation. Gamma radiation is usually emitted along with a-particles and p-particles. 

Why were Dalton s ideas about atoms considered a scientific theory, whereas the ideas of ancient Greek philosophers 

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Explain the relationship between unstable nuclei and radioactive decay. 

Unstable Nuclei and Radioactive Decay 4.11. Kinetics of simple radioactive decay... 

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