Atomic Theory

What do all of these things have in common? 

 Tofu, Elephants, Empire State Building, your hand, chocolate, peaches, frogs, brick, trees, dirt, salt, water? 

 All are made of atoms.  It is incredible to realize that roughly only 1000 different types of building blocks are responsible for the variety we see.  

 1000?  We thought there were roughly only 100 different types of atoms.  Look at the periodic table!

 Ah!!!    We do have a lot to learn.    Here is what we are going to be investigating….

 We’ll begin with a brief look at the development of the history of atomic theory.  What led people to believe that atoms existed.  From there we will describe the parts of the atom you have encountered many times before:  the electron, proton, and neutron. 

 With respect to the electron, our emphasis will be on understanding where those pesky particle/waves are found.  We’ll investigate the idea of having quantized energy levels… discussing quantum numbers and how the atoms compare with one another with respect to their electron's locations.  We’ll do a little bit of electron addressing, that is, we will describe electron locations by writing electron configurations, orbital notations and electron dots for any number of elements.  Our focus though is realizing how the number of electrons in the outer energy level, the valence level, determines the chemical properties of the atom in question.  We’ll see again and again throughout the year how it is just this physical location with respect to the nucleus that conveys special properties to the atom.

 For the most part we will discuss protons and neutrons together.  We’ll spend some time symbolizing different atoms.  In this discussion, not only will we learn how ions are formed and how ions differ with respect to their subatomic particle composition, but we will also describe isotopes, reviewing concepts of mass numbers in the process.   In this discussion, it should become clear how there are many different types of atoms that are present in the universe, atoms of a particular type of element differing perhaps only with respect to the number of neutrons in the nucleus. 

 We will also be focusing on what makes the nucleus stable or unstable.  We’ll investigate the different types of radiation that occur as a result of instable nuclei and work to understand why those nuclei might be unstable.  We’ll look into nuclear change, writing nuclear equations, and briefly describe some different nuclear applications, ranging from power generation, geologic dating to medical or home uses. 

 The background is picture of nickel atoms “images” as revealed by a scanning tunneling microscope.    Part of the picture appears on p. 72 of the Holt Chemistry 2004 textbook that we are currently using.