# Hon Chemistry 10-25-18 Oxidation Numbers & Help Session

HON CHEMISTRY: So how are the chemical formulas and chemical names coming? With oxidation numbers, you now have a few guidelines to help polish up what you already know!

And don’t forget to add one more thing to your “make sure you memorize for the test” list: polyatomic ions, chemical names and formulas for common substances, binary acids, oxyacids, prefixes, and from today oxidation rules. Oxidation rules! We’ve really already been using oxidation numbers, you just didn’t know it! 🙂

But does it all matter? These complicated rules about naming compounds, I mean. Let’s find out tomorrow in lab!

## 15 thoughts on “Hon Chemistry 10-25-18 Oxidation Numbers & Help Session”

1. M Elkins HC6 says:

This week I learned about naming binary ionic and molecular compounds, assigning oxidation numbers, and how to apply the polyatomic ions I memorized to those things. When assigning an oxidation number to a polyatomic ion, you do not count the number of charge in the ion. You have to find each elements charge. For example, with PO4-3, (I am not sure how to do super and subscripts, but I wrote the ion how you should say it.) you would multiply the 4 by -2 since oxygen (O) is in group 16, and you’ll get -8 for oxygen’s oxidation number. Phosphorus'(P) oxidation number has to be +5 because +5 + -8 = -3. Phosphorus and oxygen’s charges should equal -3, so that is why the two charges are added together.

2. T Harper HC6 says:

This week I learned how to assign oxidation numbers. In the chemical formula CO2 -3, I am going to find the oxidation number for each element. Since the formula has a charge of -3, the charges of carbon plus oxygen have to equal -3. I know that oxygen has a charge of -2. I have to multiply -2 times 3 since there are three oxygen to give me -6. Therefore, the charge of carbon has to be +3 since the two charges have to add up to be -3. +3 + -6= -3. So, the oxidation number for carbon would be +3, and the oxidation number for oxygen would be -2.

3. J Puleo HC6 says:

This week we learned how to name and write formulas for binary ionic compounds, binary molecular compounds, and molecules with polyatomic ions. These are used to name chemical formulas so that other scientists know what chemical you are talking about. For example, if you are dealing with the compound CO2, you have to know the elemental symbols and the general distribution of elements in order to know that there are no metals in this compound. This then tells you that it is a molecular compound which means that the prefix system is valid. Also, you need to memorize the prefixes in order to assign them correctly to the elements in this compound. Additionally, you have to know that the second element’s ending is replaced with an -ide. After all of this is established, you can name the compound. In this case, the compound’s name is carbon dioxide.

4. G Taylor HC6 says:

This week I learned about oxidation rules. I can apply this knowledge of oxidation rules to balance chemical equations, and to find the oxidation numbers of compounds in chemical equations.

5. B Luff HC6 says:

This week I learned how to read and write chemical formulas, as well as determining the oxidation numbers of elements in compounds. This can be used to read different chemicals in substances and figure out of their oxidation numbers. For example, the oxidation number for fluorine is always -1, so in a binary molecular compound of HF, the charge of hydrogen is +1, which it almost always is if it is not combined with a metal. These rules will definitely help me not only in this class, but in higher-level science classes and moments in the real life as well.

6. M Stevenson HC6 says:

This week I learned how to assign oxidation numbers. For example, if you were to find the oxidation number of each element in SO4-2, you would first write _____+_____=-2. All of sulfur plus all of oxygen must equal -2 since in polyatomic ions, the total charges of each element must equal the charge of the polyatomic ion. The charge of oxygen is -2 since it’s in group 16, and when you multiply -2 and 4, you get -8. Therefore, the sulfur’s oxidation number must be +6 because +6+-8=-2. Oxygen’s oxidation number is -2 because there are 4 oxygens.

7. J Jennings HC6 says:

This week I learned how to name componds using the prefix system. For example the compound P4O10 would be named tetraphosphorous decoxide. The number after the element determines the number of atoms of that element. The prefix for 4 is Tetra, and the prefix for 10 is deca. You then put these prefixes before the name of the element that they go with.

8. M Lott HC6 says:

This week I learned how to name compounds using the prefix system. You add numerical prefixes to the names of the elements to indicate the number of atoms present. With the second element, you change its ending to -ide. For example, H20 is dihydrogen monoxide and AsCl3 is arsenic trichloride. I also learned how to assign oxidation numbers and the set of rules that are applied to oxidation numbers. Like how the oxidation number of an uncombined element is zero or how Fluoride is always -1. In UF6, all charges must add up to 0. Since fluoride is -1 and there are six molecules , its total charge is -6. Uranium’s charge must be +6 because +6 + -6 = 0.

9. J Fowler HC6 says:

Over the past two weeks we have learned how to formulate, name, and write chemical formulas as well as determine the oxidation number for an element in a chemical formula based on oxidation rules. Since learning this information I have become more aware of the chemical composition of substances used in everyday life. For instance, the other night I was watching a medical tv show drama and one of the doctors ordered calcium chloride to be given to a patient. In my head I was thinking calcium chloride is composed of one calcium atom bonded to two chlorine atoms so the chemical formula would be CaCl₂. I also learned that different comounds can be composed of the same elements with atoms of different charges. For example, hydrogen and oxygen compose dihydrogen oxide and hydrogen peroxide.

10. M Roberts HC6 says:

This week I learned how to read and write chemical formulas as well as all the oxidation rules. Using the oxidation numbers of the different elements of a compound, you can figure out the composition of molecules and ions. This helps you understand what common substances like chalk, salt, and water are made of on a molecular level. These oxidation rules and oxidation numbers can also help you understand why elements react the way they do with other elements. These formula rules will be the basis of my learning in chemistry, just as much as they are the basis of everything in this universe.

11. C Fox HC6 says:

This week I learned about oxidation numbers and there rules. We learned the exceptions and learned how to assign them to each element in a compound.

12. S Davis HC6 says:

This week I learned about oxidation numbers and rules, ion rules, acids, and compound rules. It was difficult at first but some things became easier with lots of practice. I need to work on writing chemical names and formulas for our pretest on Monday.

13. W Hooker HC6 says:

This week I learned to read and write in binary compounds. Sulfur hexafluoride is the prefix name of the compound. There is only one atom of sulfur because of the understood mono- prefix. Mono- means one. There are also six fluoride atoms because the prefix “hexa-“ means six. So the compound is one sulfur atom combined with six fluoride atoms.

14. B Cook HC6 says:

This week I learned how to write the chemical formulas for binary compounds. First you need to find the charges of the two elements in the compound. In the compound Li2O Lithium’s charge is +1 and oxygen’s charge is -2.The next step is to use a process called crossing over. After you have crossed over the chemical formula will be Li2O. Now divid the subscripts by their greatest common factor which in this case would be 1 so no change. Finally to check your work, multiply the each elements charge by its subscript(+1 x +2= +2 and -2 x +1= -2). If the product’s sum equals zero then you have wrote the formula correctly(+2 + -2=0). So Li2O is the correct formula for Lithium Oxide.

15. O Davis C3 says:

So, I would rate myself a 4/5 for this week. I got every assignment in on time I thin and I’ve been picking up on what you’re teaching recently. The only thing is this stinking webpost hat I keep on forgetting to do. I am going to have it posted on time this week. Sister signing off 🙂