7 Lab Protocol: Fundamentals of Chemistry

Exercise 1: Draw a Bohr Model for a Carbon-12 atom

Read and discuss the pre-activity questions on your data sheet with your group. Complete answering all questions before moving to the next activity.

1. Carbon has an atomic number of six (6). This means all atoms with 6 protons in the nucleus are carbon atoms. How many protons are present in one Carbon-12 atom?

2. Isotopes are different versions of the same element. Two atoms are isotopes of one another if they contain the same number of protons but have different numbers of neutrons. Therefore, different isotopes of the same element will have a different atomic mass = # of protons + # of neutrons (a proton and a neutron are equal in atomic mass). Carbon-12 refers to a carbon atom with an atomic mass of 12. How many neutrons are in one Carbon-12 atom?

3. When thinking about an atom, we will assume that it is uncharged unless we are told otherwise. To be uncharged, the carbon-12 atom must have the same number of electrons as it has protons. How many electrons will be part of the uncharged Carbon-12 atom?

4. Atoms can have multiple electron shells. Each shell has a maximum number of electrons that it can hold: the shell closest to the nucleus is the first shell and can hold a maximum of 2 electrons; the second and third shells can each hold a maximum of 8 electrons. Since electrons prefer to be in their lowest possible energy state, the first shell is filled first followed by shell 2 and then shell 3.

How many electrons will be part of the first shell in a Carbon-12 atom?

How many electrons will be in the second shell?

How many electrons will be in the third shell?

5. The outermost shell containing electrons is called the valence shell of that atom. How many electrons are expected to be in the valence shell of a Carbon-12 atom?

6. The valence number of an atom refers to the number of unpaired electrons in the valence shell. Note that this is not the same as the number of valence electrons. The valence number can be determined by placing one electron at a time into the valence shell. If the second or third shell is the valence shell, consider it to have a north, east, south, and west position. You must put one electron into each of these positions before going back and adding a second electron. After you have done this, the number of electrons that are not part of a pair of electrons is called the valence number. (Remember that before placing any electrons in the valence shell, lower-level shells must be filled.) What is the valence number of an uncharged Carbon-12 atom?

7. The number of bonds that an atom is expected to make is the same as the valence number of that atom. How many bonds is a Carbon-12 atom expected to make?

8. Draw a Bohr model for Carbon-12 atom.  Each group member is to draw their own Bohr model and initial next to it. Include the nucleus and electron shells making sure that the number of protons, neutrons, and electrons are correct and can be clearly counted by the instructor.  Make sure it is clear which valence electrons are paired and which are unpaired.

Exercise 2: Determine the type of chemical bond

In this activity, you will practice identifying what type of chemical bond two atoms are likely to make depending on the difference in electronegativity between them. Complete the activity labeled Exercise 2 on your data sheet with your group.

Complete the following table in your data sheet.

Complete the following table in your data sheet.

Exercise 3: Identify the model elements by color

Now, you will work with the chemistry models provided in lab. The balls in the chemistry model kit represent different elements and the connectors represent covalent bonds. Based on the number of holes per ball (which represent unpaired electrons and the potential to make a bond), indicate which color of ball represents each of the following elements:

Phosphorus:

Carbon:

Hydrogen:

Nitrogen:

Oxygen:

In this model kit, the pieces used to represent single covalent bonds are short and rigid. The pieces used to represent double covalent bonds are long so that they can bend a little bit. Find examples of each in the kit.

Exercise 4: Build functional groups

For each of the following functional groups, build the functional group using the correct elements, you may take a photo if you like, but your instructor will need to initial your data sheet in order to move on. You may use the tables below or your course textbook to help you build the functional groups.

1. Methyl
2. Hydroxyl
3. Carboxyl
4. Carbonyl
5. Amino
6. Phosphate

Below is a table that displays the functional groups to help you accomplish this task. Note that the colors may be different than the model. Focus on the elements used.

Exercise 5: Build an amino acid using functional groups.

There are four components that make up an amino acid:

• A central carbon, including a covalent bond to one hydrogen.
• An amino group.
• A carboxyl group.
• An R group

Using the functional groups you produced in the previous task and other model parts, build the amino acid valine, isoleucine, serine, or asparagine. Below is a table showing the atomic make-up of all standard amino acids.

Exercise 6: Build various hydrocarbons

Build each of the following hydrocarbons:

• An unbranched chain with 4 carbons and 10 hydrogens (C₄H₁₀)
• A branched hydrocarbon with 4 carbons and 10 hydrogens (C₄H₁₀)
• Chain with 4 carbons and 8 hydrogens (C₄H₈) including one double bond between any two carbon atoms
• A ring with 6 carbons and 12 hydrogens (C₆H₁₂)
• Two different structural isomers of C₄H₉OH

Exercise 7: Demonstrate hydrogen bonding

Build five water molecules (H₂O).

Lay the water molecules on the table. Line up the water molecules so that the oxygen of one water molecule is pointing toward one of the hydrogens of the other water molecule. Take a picture. Get instructor initials.

What is the name of the attraction between the oxygen of one water molecule and the hydrogen of the other?

Is this a type of covalent bond?     Circle one:         Yes                         No

What type of covalent bond is this?

Text adapted from Jacob Broderick