Lesson 5: Wrap-Up
In this lesson we took a fairly detailed look at the structure of the atom. Of particular importance was the behavior of the electrons. This behavior is determined by the magnitude of the positive charge in the nucleus and by the arrangement of the electrons in the atom. In one part, we spent a lot of time looking at the nucleus (protons and neutrons) and how that affects the identity of the element and its mass number. We then looked at how the number of protons and electrons balance each other's (opposite) charges to see if that atom has a net ionic charge. The key to understanding this section is to learn the relative masses and charges of the protons, neutrons and electrons.
We also spent time working with the relationship between Avogadro's number (6.02 x 1023 things/mole), moles, and atomic (or formula) weights.
The wave mechanical model of the atom - also called quantum mechanics - gives us the best and most accurate picture of electron behavior. In particular, it describes with reasonable accuracy what happens with the valence electrons, the outermost electrons in the atom, the electrons that are involved in chemical reactions.
In the next lesson, we will use what we have learned about atomic structure to try to understand some of the chemical behavior of the elements. For example, what is the difference between a non-metal and a metal? How do they react, how do they react differently, and why? We will also see how the periodic table of the elements arises and learn some of the different kinds of things it can tell us about the elements.
Be sure to complete and turn in the lab assignment and the problem set found in your workbook. The purpose of the lab experiment this week is to observe the flame colors of some different known samples and to identify three unknown samples based on the knowns; don't forget to include the identities of your unknown samples in the Results section of your lab report! A second purpose was to observe the spectra of some gaseous elements in the discharge tubes; be sure to include those observations in your lab report as well. Try the self-quiz and check your answers before you take the quiz for this lesson. If you need help, you know whom to contact.
Self Quiz
Atomic weights (in g/mole): oxygen 16.0; sulfur 32.1, sodium 23.0, iodine 126.9
1. Write the proper isotopic symbol for a phosphorus atom containing 15 protons and 16 neutrons.
2. Rutherford's experiment "discovered":
| a. protons | b. atoms | c. neutrons | d. nuclei | e. electrons |
3. Evidence that atoms contain electrons came from:
| a. alpha scattering experiments | b. Rutherford | c. Dalton | d. cathode ray experiments |
4. What is the weight in grams of 1.0 x 105 SO2 molecules?
5. Which atomic model allows for a larger variety of energy levels?
| a. Bohr | b. wave mechanical |
6. Fill in the blanks:
|
NAME |
MASS (amu) |
CHARGE |
|
|
negligible |
-1 |
|
proton |
|
|
|
|
1 |
0 |
7. If one mole of a compound weighs 85 grams, what is the weight of one molecule in a.m.u.?
8. Fill in the blanks.
|
SYMBOL |
#p |
#n |
#e |
CHARGE |
MASS # |
|
13N |
|
|
|
|
|
|
|
12 |
|
|
0 |
23 |
|
|
|
17 |
|
-2 |
33 |
|
66Zn2+ |
|
|
|
|
|
9. 5.7 x 10-7 moles of Hg contain how many atoms?
10. What is the weight in grams of 1.46 moles of NaI?
Self Quiz Answers
1. Write the proper isotopic symbol for a phosphorus atom containing 15 protons and 16 neutrons.
31P (a complete isotopic symbol would also include the atomic number underneath the mass number)
2. Rutherford's experiment "discovered":
d. nuclei
3. Evidence that atoms contain electrons came from:
d. cathode ray experiments
4. What is the weight in grams of 1.0 x 105 SO2 molecules?
1.1 x 10-17 g
5. Which atomic model allows for a larger variety of energy levels?
b. wave mechanical
6. Fill in the blanks:
|
NAME |
MASS (amu) |
CHARGE |
|
electron |
negligible |
1- |
|
proton |
1 |
1+ |
|
neutron |
1 |
0 |
7. If one mole of a compound weighs 85 grams, what is the weight of one molecule in a.m.u.?
85 a.m.u.
8. Fill in the blanks.
|
SYMBOL |
#p |
#n |
#e |
CHARGE |
MASS # |
|
13N |
7 |
6 |
7 |
0 |
13 |
|
23Mg |
12 |
11 |
12 |
0 |
23 |
|
33S2- |
16 |
17 |
18 |
-2 |
33 |
|
66Zn2+ |
30 |
36 |
28 |
+2 |
66 |
9. 5.7 x 10-7 moles of Hg contain how many atoms?
3.4 x 1017 atoms of Hg
10. What is the weight in grams of 1.46 moles of NaI?
219 g of NaI (the formula weight of NaI = 149.9 g/mol)