After Module 7, we move into Module 8. Module 8 discusses molecular structure which should have been covered in the very first week of class. This module is important. It is important to understand how atoms bond. Understanding this module is important for all Chemistry.
I do have good news. It isn’t hard. I touched on it a little in my discussion of Module 7. If you have explained the periodic table in detail, your student shouldn’t have any difficulty with this module.
I wrote about nomenclature in my post about on Module 3.You can find some links there to help you write the chemical formulas. Remember that all the atoms want 8 valence electrons in their outer shells. It makes them happy. They want to be like the noble gases. The cool kids on the block. They want to grab electrons. Some more than others. Some are happy to share as in a covalent bond. Some are takers as in an ionic bond.
It is easiest for me to remember that two non-metals form covalent bonds, and a metal and a non-metal form an ionic bond. If you are still have trouble check out this page to compare the two. Here is a quiz to check your knowledge.
Drawing Lewis structures is not difficult. You only need to know the number of valence electrons which you get from the group number of the element. That is all you have to know.
For example, let’s take Oxygen.
Oxygen is in Group 6A. This tells me that Oxygen has 6 valence electrons. See? Easy. (My lovely drawing in Paint)
I just drew six, happy little dots around an oxygen atom. Now, I know that oxygen is a diatomic atom, meaning that they never go it alone. So, if I want to draw the Lewis structure for the oxygen bond, I just match up the lonely electrons.
You don’t need to draw all the electrons after you know how they are bonded. It is redundant. We know all the other electrons are happily paired together.
Let’s do one more because it is fun. How about PCl3
Phosphorus has three unpaired electrons. No, you can’t pair up two of the singles. There must be an electron at each of the spots on the compass before you start pairing them up. If I were to pair up two electrons, there would be an empty spot. This is how we draw the Lewis structure in order to get the correct bonds.
Chlorine has one unpaired electron. Phosphorus wants three. One chlorine atom can’t give a Phosphorus atom three of its electrons. Remember, it wants to have a full 8 as well. (the octet rule). So, instead two more Chlorine atoms join the party.
Does that just look like a bunch of red dots? It does. But let’s draw the bond lines.
Remove the rest of your paired electrons.
This is my first attempt at drawing in paint. Please don’t laugh. I wanted to have a picture sitting at the top of my post. I get nervous about grabbing pictures from other places. To avoid any kind of issue, I made my own. It is sad but colorful!
After telling you that I was going to move into Module 4 after Module 3, I changed my mind. I decided that I wanted to move into Module 7. I am glad that I did. We had good results. I think it is because we have been focusing so much on the periodic table that this was an easy module to move into.
What is important in Module 7.
- Electrical Charge. Like charges repel and opposite charges attract. This is one of those things that the kids should already know if they have played with magnets at any time in their lives. The experiment is unnecessary, and we had little success with it when we did it. Instead watch this corny video. It is likely that you won’t even need to explain this topic any further.
- Mass number. Now, if you are like me, you have already discussed this in-depth with the kids. They should know what the mass number tells and be able to tell how many protons, electrons, and neutrons any atom has.
- Isotopes. It is important to understand that isotopes are atoms that have the same number of protons, but different numbers of neutrons. Carbon-12 and Carbon-13 are still Carbon atoms. Carbon-13 just has one more neutron than Carbon-12. I don’t think he does a very good job of explaining the isotopes. Basically teach the kids how to write the isotopes and determine how many protons and neutrons an element has based on its symbol.
- Atomic Structure. He spent a lot of time on this and made it much more wordy than it needed to be, in my opinion. It is important to know that J.J. Thompson discovered electrons using the Cathode Ray Tube. He believed the electrons were suspended in the atom like plums in plum pudding. This was later disproved by Ernest Rutherford. His experiment led to the planetary model of the atom which later led to Bohr’s model of the atom.
- Light. Dr. Wile includes light in this module so that the student will understand Rutherford’s experiment and how it let to the Bohr model. The math isn’t difficult and shouldn’t be too difficult to teach. WARNING: In this module, he tells the kids that the primary colors are red, blue, and green. My daughter was up in arms. This is not wrong. I did a bit of googling and the primary colors are different depending on which method of combining colors you use. With the additive method, the primary colors are red, blue, and green. When we combined colors in Kindergarten we used the subtractive method. Red and blue make green. Right? This was a bit confusing. Physics classroom has a good explanation. Here is another very in-depth discussion on color. So what the kids learned on Sesame Street is not wrong, but when we speak of light and not pigment the primary colors are red, blue, and green.
It is important to remember that all forms of matter want to stay in their ground state. This is the lowest possible energy state. This means that electron want to be in the lowest orbital possible as close to the nucleus as they can. Orbitals are the paths of the electrons around the nucleus. There are s, p, d, and f orbitals. I was going to explain it, but Chemistry for Competitions does a nice job of explaining the orbitals. A MUCH better job than I could do. Honestly, it is more than you will need for this course, but so what. Let’s aim high, shall we?
Before you start, print out this chart of electron configurations. It is much better than the one in the book. If you use that chart, you shouldn’t have any trouble writing the electron configurations. Don’t use the chart forever and don’t give it to them for the test. It is a good tool to use while they are learning about the orbitals, but writing electron configuration isn’t difficult. I do let my kids use a regular periodic table. I was going to explain how to write the configurations, but he does a fine job doing it in the book.
I want to mention the book, “Atoms, Molecules, and Compounds” by Phillip Manning. I notice on Amazon that it is only available as a Kindle download, but maybe your library will have it. It has a very good explanation about orbitals and writing electron configurations. It was helpful for me to see another presentation to refresh my memory. I found it at my library.
Beware rant ahead…
I am looking ahead to Module 8. So here it is. How to write chemical formulas properly. Do you see my frustration? Module 8. 16 weeks into the course and now he is talking about valence electrons and nomenclature. I am banging my head against the wall here. I know that you can’t see it, but I am. He is giving baby bits of information in a module. Molecular structure and atomic structure could have easily been squished into one module. These are sophomores in high school for crying out loud. Ok. I said my piece. One more thing while I am ranting. He says that electron configurations are not a worthless exercise. “They have a very, very deep meaning to a chemist.” Really? Very, very deep? Not just a little deep? That kind of writing is fine for me, but I am not writing a high school textbook. Ok, I am done.
I think that covers the module. It isn’t a very difficult module, and the math isn’t too tough. Remind your student to watch the units. Make sure they write their answer with a unit attached. Also watch significant figures. Good luck!
Now that we have finished Module 3, I can finally write about how we tackled the module. There are two important laws covered early in the module, The Law of Mass Conservation and The Law of Definite Proportions. I thought it was odd that these laws were covered before the periodic table, but it seems that they are covered early in most textbooks that I glanced over.
The Law of Mass Conservation states that matter can not be created or destroyed; it can only change forms. Great! This makes sense when you think of a pot of water. Place a pot of water on the stove, add some heat, and notice what happens. The water boils away, but only because it changed forms. We didn’t destroy the water. We converted it to water vapor using heat. Wile uses the example of a fireplace. The math is easy because it is simple addition and subtraction. The totals must be equivalent on both sides of the equation. Simple algebra will solve for any unknown.
I have to stop here. Since I am talking specifically about the Apologia book, I need to make a note about his problem 3.1. He asks how much oxygen was used up by the wood while it burned. Ok. Fine. We know that fire needs oxygen and fuel to burn. But the words “used up” in his question are very misleading. The oxygen is used, but in the reaction it is converted to carbon dioxide and water vapor. Here he is saying that matter can’t be destroyed and then asking the kids how much oxygen is “used up”. It was very confusing to my daughter. I think it is confusing because they haven’t had any exposure to chemical equations. So, while the fire place is a good example that she could easily grasp, I needed to explain that oxygen was used and changed not “used up”. (Plus, it is highly likely that there was still oxygen in the room and the wood just burned away completely making it the limiting reactant which is a topic they will learn later. But geez, the whole thing bugs me.) I think it is pretty important that you make a couple more practice problems. You can use the same problem. Change the numbers and the amount of substance you are trying to find.
He then goes on to talk about the periodic table, which if you are like me, you have already done.
We then talked about the Law of Definite Proportions which states that the proportion of elements in any compound is always the same. This law is based on ratios. Hopefully, your student(s) has had some exposure to ratios and scale factor in their algebra because it becomes very helpful to do the problems.
I don’t think the math is difficult for these problems, but what helped my daughter was thinking in terms of scale factor. For example, if you have picked 3 bushels of apples, but have to pick 9 bushels of apples by the end of the day, you need to increase by a scale factor of 3. In Chemistry, if you know what you need to make 21 g of lime, but you want really want 55 g of lime, you need to increase each of your reactants by a scale of 2.6. My daughter was confused thinking she had to increase it by adding more calcium or something rather than just a scale – a number without a unit. Once I had her thinking in terms of scale factor it made much more sense.
Again. You need to give them more problems. Doing one on your own problem is not enough to fully understand the concept. Practice!
The rest of the module is fairly easy, but I expand on it a bit. It is increasingly frustrating to my kids when he says “you will learn more about this later”. He gives them a basic knowledge of ionic and covalent. Then tells them there are some exception, but don’t worry about it now. Gah! I guess it is necessary, but it is frustrating.
In this module, he gives the very basic idea of naming compounds. I love his paragraph about naming covalent compounds. (not really) NaCl will always be NaCl not Na2Cl or anything else. Why? Why, mom? Why not? Ugh. Of course they want to know. If he took the time to explain about how the compounds form, it makes it pretty easy that explains it pretty well. Since I took the time in the first module to explain the idea of electrons and charges of the elements, it wasn’t difficult. Ionic compounds want to be stable. The non-metal will grab electrons from the metal to fill up their outer shells. The metal is happy to give them away. Usually the metal now is happy because it doesn’t have any extra electrons in its outer shell and the non-metal is happy because its outer shell is filled up. It makes a lovely ionic compound. In NaCl, the sodium has one electron in its outer shell. It has a +1 charge. Chlorine has 7 electrons in its outer shell. It has a -1 charge. If Chlorine takes that one electron from sodium, everyone is happy and it is a stable compound. THAT is why NaCl is formed.
Take the time to practice this with the kids. Make other compounds. Try Potassium flouride. Potassium (a +1 charge) has one it wants to give away and flouride (a -1 charge) wants one. Ta-da! This is how to write ionic compounds. It gets trickier with the transistion metals. Here is a handy-dandy video for you to watch.
In his example, he gives the students Al2O3 to name. It is aluminum oxide. Why are there 2 aluminums and 3 oxygens? Because Aluminum has a +3 charge and Oxygen has a -2 charge. Aluminum is a metal in the 3rd group. That is how I know. Oxygen is a non-metal in group 6. It has a -2 charge. That is how I know. In order to make everyone happy, oxygen wants wants two to be full, but aluminum has three to give away. So another oxygen comes along to take that one, but it isn’t happy because it still needs one more. So, aluminum brings that one but still has two left over. This gives us our third oxygen that will take the last two. Does that even make any sense? Thus, there are two aluminums and three oxygens.
Make lots of practice problems. Lots and lots. They need the practice. To make it easy, stay away from the transistion metals. But if you are really brave, this video explains it for you.
I do not think it is too much to ask of the kids to understand how compounds are named. It isn’t difficult, and makes things easier later on.
Good luck!! One more website for you.
We did not go to module 4. We have moved into module 7. I will write about that when we are finished.
The other day Applie posted on her blog that she is planning to teach Apologia Chemistry at her co-op next year. She is gearing up to teach and has found the Apologia book a bit confusing and heavy on the math. I have mentioned before that I am not a big fan of the Apologia Chemistry book. In fact, I am less of a fan than I was when I wrote that post, but I have the book and we are going to use it. I just have to tweak it. A lot. I don’t have the plan done for my girl’s entire year of Chemistry, but I do have the first couple of weeks. Maybe if I am motivated I will blog about it as we go along. Hence, the Part 1 in the title. We will see. But at least I can give a start.
I do start with Module 1.
What is important in Module 1
- Mass. It is important for the student to understand the concept of mass. The experiments are lame, but they make the point. Mass and weight are not the same thing. This is important. The book talks about it a bit, but the point needs to be driven home.
- Units of measure. I love the metric system. Love it! Why our country won’t get on board and quit using the English units is beyond me, but that is beside the point. Students need to be comfortable with basic units of measure. If they aren’t comfortable yet, they should make a cheat sheet for handy reference of equivalent measures. Donna Young has a great one. The goal should be to memorize them, but as they practice that should come.
- Unit multipliers. This is extremely important. Students have to be comfortable with this. One pet peeve that I have Dr. Wile briefly mentions that 1 cc is equivalent to 1mm. But he just throws it in there. It is kind of a “oh yeah, by the way”. Lame. It is a handy conversion and used frequently, and in advanced sciences FREQUENTLY. (side note: I worked in a biochemistry lab in college. I was working with very small amounts at times and it was always in cc’s.)
I am going to stop here and discuss unit multipliers for a second. I do not like the way that Dr. Wile explains them. I am sure it is a personal perference. His way works and it is fine, but I don’t like it. If I was tech savvy, I would make my own YouTube video, but I am not. If you want to hear someone talk it out, here is a handy video of it.
- Significant figures. Again important. Do you see how much stuff he crams into this module? He does a fine job explaining them, but the kids need more practice. There are a bunch of different applets online to practice. Just google for it. Find one that has what you want. This is a MUST. If they don’t grasp this concept now, it will haunt them the entire course. They must memorize the rules.
I want to say something about the experiments in this module. They are very lame, but they have a purpose. I did not make my daughter write them up. We did them to prove a point. I used experiment 1.4 mainly to practice measuring and reading liquids in a graduated cylinder. There is value in that. If you have been homeschooling awhile, I am sure your kids get the density concept. Why he includes density in this module is beyond me. There is plenty in this module for the kids to remember. However, they need to memorize the formula, be able to use it appropriately, convert the units, and determine significant figures. Help them do that.
So, that is Module 1.
I see that this is going to be a long post, but I want to talk a little about where I go now. I do NOT going into the second module. You can if you want. It is all just math, but I found it frustrating to jump right into it. It is a module that can be done at any point in the course. If you have a student that struggles with Algebra, maybe wait until later in the year when their math skills are a bit stronger or until the summer cobwebs have cleared.
Next I begin discussing the periodic table. The periodic table is a beautiful table that has beautiful order. I don’t think that point is ever brought to the kids’ attention. Understanding that order makes things so much easier. There are tons of YouTube videos that explain this. I can’t find the one I really like. Typical. But there are some good ones there.
First of all make a black and white copy of the table on the inside cover of the book. Have the kids get their colored pencils ready. Color the table explaining the difference between metals, non-metals, and noble gases. You may need to find another reference. I use the Usborne Science Encyclopedia. What does everything in the box mean? Answer all these questions now.
It is also imporant to understand the periods and groups on the table. What do these mean? The kids should have some understanding from previous classes about protons, neutron, and electrons. If they don’t, you need to cover this now. They should understand that electrons are in shells surrounding the nucleus of the atom. The Usborne Science Encyclopedia again gives enough information for this point.
One thing I like to point out that the elements in their groups behave in similar ways. For example, the metals in group one (this excludes Hydrogen because it is not a metal) all react with water in a similar way. What is intersting is that as you move down the periods they become more reactive. You can mix Lithium with water, and you have a small reaction. But if you mix Cesium with water you hae a lovely, violent reaction. Watch this video for a good demonstration. See? Fun!
Next I explain what the periods and groups mean. This is so important for later. We know that the electrons of an atom are arranged in shells. The elements in each period have the same number of shells. In period one we have Hydrogen and Helium. They have one shell. In period 2, the atoms have two shells. And so on. The elements in the same groups have the same number of electrons in their outer shell. For example the atoms in group VI all have 6 electrons in their outer shell. This is enough information for now.
Now I am ready to teach Module 3. Except we cover much more about naming compounds. In fact, it really, really bugs me how little time he spends on this. He jumps into chemical reactions in the following module before they are comfortable with the nomenclature. Irritating!! I am just getting ready to cover nomenclature with my daughter. As I work on that, I will keep notes and I will make a page for links that teach nomenclature. Now is the time to bring out the chemical beads and play with them. After they are comfortable with nomenclature it is fine to move to Module 4.
Sigh. As I am looking more and more at this book, I find myself liking it less and less. I think I will write a post about nomenclature. Just not today. I feel so bad for my oldest. That I made him suffer through this.
End note: This took me much longer than I had anticipated. I am not sure how this will work. I think I will make the next posts a lot more simple.