Chemistry Lab 3
Molecules and Chemical Formulae
(With Rules)
Essential Question:
How do we construct molecular compounds?
Materials:
PASCO Molecular Model Kit
Background:
Paper, glass, plastic, metal, flesh, and almost all the material on Earth is made of atoms, that is, elements. There are only 91 elements on Earth from which all substances can possibly be made. In fact, only six elements make up almost everything around us. How does such a wide variety of substances get made from only a few elements? Well, the English alphabet contains only 26 letters, and yet we can spell thousands of words. In the same way, the variety of substances depends on the way the atoms are put together.
Safety:
Don’t put the parts of the model in your mouth.
Read this:
Chemistry is an enormously complex subject at its base, so it is surprising that it can follow some simple laws in most situations. For example, in most molecules, a given atom tends to form a specific number of bonds. For example, a carbon atom makes four bonds, a nitrogen atom makes three bonds, and an oxygen atom makes two bonds.
When one atom bonds to another, it may have a single bond, a double bond, or a triple bond.
Note this:
Note the following assignment of atoms:
Color / element / symbol / number of bondsblack / carbon / C / 4
white / hydrogen / H / 1
red / oxygen / O / 2
blue / nitrogen / N / 3
green / chlorine / Cl / 1
purple / iodine / I / 1
Procedure:
1. Use the molecular kit to build a possible structure for each of the following molecules. Make sure you follow the rules for how many bonds connect each atom.
2. Draw your structure, using letters in place of the colored model atoms. There may be more than one answer.
Analysis:
Questions:
1. Which of your models used double bonds?
2. Which of your models used triple bonds?
3. Did you notice any patterns in the way you drew your diagrams? (It is okay to say, “No.”)
Analysis: (Larger molecules)
In the spaces below draw two unique structures for C4H8O2. (These are called “isomers.”)