ELEMENTS

OBJECTIVE:
Identify electrons, protons and neutrons and explain how they combine to form an element.

BACKGROUND:

Elements are composed of electrons, protons, and neutrons.  Since the atom appears neutral if observed form the outside, the magnitude of both charges must be equal.  The nucleus occupies the center of the atom and comprises positive particles (protons) and electrically neutral particles (neutrons).  Like the planets around the sun, negatively charged particles called electrons, orbit the nucleus.  This is the atomic shell.  The number of electrons is equal to the number of protons.

The atomic number refers to the number of protons per atomic nucleus.  Atomic weight is the combined weight of the protons and neutrons.  You can subtract the atomic number from the atomic weight and find the neutrons.  The number of protons equals the number of electrons.  Each of the elements have not only a unique atomic weight and number but also have a structure in which they are constructed.  In  this activity the students will construct different crystalline structures using googolplex to develop a feel for the crystalline structure.  They will then use the periodic table of the elements to count the number of different crystalline structures.  They will then decide if the crystalline structure or the atomic number/atomic weight is  the most unique characteristic of an element.  The atomic number/atomic weight is characteristic of the element more than the crystal structure.

PROCEDURE:

Follow your lab sheets. Reference information is available in Structure of Molecules with Googolplex pages 2-11.

MOLECULES  

OBJECTIVE: Understand how elements combine to form molecules.

BACKGROUND:

Atoms of different elements combine to form molecules of substances.  These molecules are held together by forces called "bonds."  There are various types of bonds and the way that these bonds are arranged is unique to that substance.  We will be concerned with two types of bonds:  ionic and covalent.

Ionic bonds are formed when electrical charges (positive and negative) come together to form neutral substances.  Salt is the best example of an ironically bonded substance.  Salt consists of sodium ions (+) and chlorine ions (-).  When these + and - ions come together they form salt, a stable substance. 

Ionic substances such as salt possess several characteristic properties.  They are usually brittle substances with high melting points.  They are also crystalline, meaning that the solids have flat surfaces that make characteristic angles with one another.  The vast majority of chemical substances do not have the characteristics of ionic materials; we need only think of water, gas, banana peelings, hair, and plastic bags.  For the very large class of substances that do not behave like ionic substances a different model for the bonding between atoms is required.  This type of bonding is called covalent bonding. 

PROCEDURE:

In this exercise the students will make models of four molecules:  water, hydrogen, methane, and hydrogen chloride.  Reference information and instructions are located in Exploring the Structure of Molecules with Googolplex pages 18-20.