Chemistry Essentials for Dummies
Chapter 4. Nuclear Chemistry
In This Chapter
· Understanding radioactivity and radioactive decay
· Figuring out half-lives
· Knowing the basics of nuclear fission
· Taking a look at nuclear fusion
· Tracing the effects of radiation
In one way or another, most of this book deals with chemical reactions. And when I talk about reactions, I’m really talking about how the valence electrons (the electrons in the outermost energy levels of atoms) are lost, gained, or shared. I mention very little about the nucleus of the atom because, to a very large degree, it’s not involved in chemical reactions.
But in this chapter, I do discuss the nucleus and the changes it can undergo. I talk about radioactivity and the different ways an atom can decay. I discuss half-lives and show you how they’re used in archeology. I also discuss nuclear fission and the hope that nuclear fusion holds for humankind. Finally, you get a quick glimpse of how radiation affects the cells in your body. Don’t forget the lead shielding!
Seeing How the Atom's Put Together
To understand nuclear chemistry, you need to know the basics of atomic structure. Chapter 2 goes on and on about atomic structure, if you’re interested. This section just provides a quickie brain dump.
The nucleus, that dense central core of the atom, contains both protons and neutrons. Electrons are outside the nucleus in energy levels. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge. A neutral atom contains equal numbers of protons and electrons. But the number of neutrons within an atom of a particular element can vary. Atoms of the same element that have differing numbers of neutrons are called isotopes. Figure 4-1 shows the symbolization chemists use to represent a specific isotope of an element.
Figure 4-1: Representing a specific isotope.
In the figure, X represents the symbol of the element found on the periodic table, Z represents the atomic number (the number of protons in the nucleus), and A represents the mass number (the sum of the protons and neutrons in that particular isotope). If you subtract the atomic number from the mass number (A - Z), you get the number of neutrons in that particular isotope. A short way to show the same information is to simply use the element symbol (X) and the mass number (A) — for example, U-235.