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    "What is an Atom?" Exercise Sheet for Science Students

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    Take a clear balloon. Add one BB and blow up the balloon to about the size of a softball, then tie it off.

    1. What is an atom? What is the charge of a proton, neutron, and electron? What does this balloon represent? What does the BB represent?

    2. The diameter of a proton is approximately 1 x 10^-15 meters. The diameter of a hydrogen atom is 1 x 10^-10 meters. If we could scale up the nucleus of a hydrogen atom (the proton) to a size just barely visible, say a dot on the chalkboard (maybe 1 mm or 1 x 10^-3 m), what would the diameter of the atom be? This tells you how much space there is between the nucleus of an atom and its electron.

    3. Physicists say that if you collapsed all of the visible universe by taking away its space, it would fill a space a little larger than your thumb! Can you imagine that? Now take 2 colored balloons, one small and one large. Put 2 BB's in the small balloon and 6 in the large balloon. Place the small balloon inside the large one and blow it up to the size of a baseball (and tie it off). Then blow up the large balloon to the size of a football and tie it off. What does this represent?

    4. Electrons in an atom are arranged in energy levels or valences. A certain number of electrons fit in each energy level, with each level having more energy.
    The 1st energy level holds ______ electrons.
    The 2nd energy level holds ______ electrons.

    5. Look at the colored balloons. How many electrons are in the first energy level of Oxygen? How many electrons are in the second energy level for Oxygen?

    6. Do electrons always stay a fixed distance from the nucleus? If not, give an example.

    7. What is a molecule?

    8. Make a water molecule (H2O) using balloons (you will need to make one more atom).

    Oxygen is very electronegative - it wants 2 more electrons in its outer shell. In a water molecule, the nucleus of the oxygen atom will pull the electrons from the hydrogen atoms so that they are closer to oxygen. This gives the oxygen atom a slight negative charge and the hydrogen atoms a slight positive charge. Therefore, water is a polar molecule. The polarity of water gives it some unique characteristics. Define the following terms:
    - Polar
    - Nonpolar
    - Cohesion
    - Adhesion
    - Hydrophilic
    - Hydrophobic
    - Solute
    - Solvent

    9. What does pH mean? What is the pH range for an acid? For a base? For a neutral solution?

    10. Based on the results what was the unknown solution? How did you determine this?

    11. What is a neutralization reaction?

    12. What is the difference between a strong acid (or base) and a weak acid (or base)?

    13. Fill out the chart for the available substances. Determine whether each is an acid, a base, or is neutral and estimate the pH for each.

    Substance Acid/Base/Neutral pH
    A (light pink)
    B (pink)
    C (red)
    D (blue)
    E (blue like purple)
    F (light blue)
    G (purple)

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    Solution Preview

    1. An atom can be described as an extremely small particle that is the basic unit of matter. I believe that the balloon is intended to represent hydrogen, the simplest atom. Note that this representation does not include a nucleus (the central portion of an atom which contains one proton for the case of hydrogen). The BB represents hydrogen's lone electron traveling around the nucleus.

    2. Let's use a ratio to work out this problem:

    Diameter of proton = Diameter of chalk dot proton
    Diameter of hydrogen atom = Diameter of chalk dot atom

    1 x 10^-15 meters = 1 x 10-3 meters
    1 x 10^-10 meters = Diameter of chalk dot atom

    Diameter of chalk dot atom = 1 x 102 meters or 100 meters

    3. This is a model representation of an oxygen atom. It would look like this if drawn. Note that the second energy level (second ring around the nucleus) can hold 8 electrons, although it only holds 6 in the case of oxygen.

    4. The 1st energy level holds __2___ electrons.
    The 2nd energy level holds ___8__ ...

    Solution Summary

    This solution includes over 650 words and provides answers and explanations for 13 questions related to basic chemistry.