## Oxidation Sapling 9

$FC=V-(L+\frac{S}{2})$

Brandon Gruender 3F
Posts: 91
Joined: Wed Sep 30, 2020 10:03 pm

### Oxidation Sapling 9

Using number 9 in the sapling hw as an example, how do you find the oxidation number? And how do you know which structure is applies to? Thank you!

Nathaly Cruz 2D
Posts: 55
Joined: Wed Sep 30, 2020 10:06 pm

### Re: Oxidation Sapling 9

I had the same question. When I was doing the problem on sapling, I got it wrong then it told me that each oxygen atom had an oxidation number of -2. Since there are 4 oxygen atoms, the oxidation number was -8. However, all the oxidation numbers added together must equal the formal charge which in this case was -1. Therefore, -8 + _____ = -1 so the oxidation number was 7.

However, I am unsure how to find the first oxidation number.

Shivani Kapur 2J
Posts: 95
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Oxidation Sapling 9

Since there are 4 Oxygens, each with a charge of -2, the total charge from Oxygens is -8. Since the overall charge on ClO4- is -1. The charge on Cl must be +7, and that is the oxidation number on Cl.

Lucy Wang 2J
Posts: 86
Joined: Wed Sep 30, 2020 10:09 pm
Been upvoted: 2 times

### Re: Oxidation Sapling 9

The sum of the oxidation numbers of the atoms in the perchlorate ion must equal the charge on the ion, -1. When oxygen is bonded to a nonmetal other than flourine, it has an oxidation number of -2. Because there are four oxygen atoms in the ion, chlorine must have an oxidation number of +7 to equal the overall charge on the ion (-1).

-1 = -8 +7

Hannah Alltucker 3L
Posts: 106
Joined: Wed Sep 30, 2020 9:44 pm

### Re: Oxidation Sapling 9

For number nine in the homework we are given ClO4- and are asked to find the oxidation number of Cl. The oxidation numbers of the entire molecule, when added together, should add up to the charge of the molecule overall. If we look at the periodic table, we can see that oxygen requires two more electrons to get a full valence, so it will have an oxidation number of -2 (since it adds two electrons). Since we have four of those it becomes (-2 x 4 = -8). -8 would be the charge for the oxygen atoms, and we know that when we add it to Cl's oxidation numbers we will have -1. That leads us to the conclusion that Cl is 7, since 7-8=-1. For finding oxidation numbers we are normally using the groups of the periodic table to determine how many electrons they want to gain or give to reach a noble gas state.

A few rules for finding oxidation numbers
-The oxidation number of a free element is always 0.
-The oxidation number of a monatomic ion equals the charge of the ion.
-The oxidation number of H is +1, but it is -1 in when combined with less electronegative elements.
-The oxidation number of O in compounds is usually -2, but it is -1 in peroxides.
-The oxidation number of a Group 1 element in a compound is +1.
-The oxidation number of a Group 2 element in a compound is +2.
-The oxidation number of a Group 17 element in a binary compound is -1.
-The sum of the oxidation numbers of all of the atoms in a neutral compound is 0.
-The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion.

Some molecules have special cases, like H2O2 where O has an oxidation state of -1, but for the most part we can go by the periodic table unless otherwise noted.

905579227
Posts: 44
Joined: Wed Sep 30, 2020 10:01 pm

### Re: Oxidation Sapling 9

Wait I dont know if anyone has said this but the simple answer is -8+7 = -1.
Hope that helps.

Anastasia Yulo 1C
Posts: 90
Joined: Wed Sep 30, 2020 9:47 pm

### Re: Oxidation Sapling 9

Sum of oxidation numbers for a neutral compound is always 0. Sum of oxidation numbers for a polyatomic ion is the ion charge.

When calculating oxidation numbers, remember that group 1A elements are always +1, Group 2A are always +2, Halogens are usually -1 (positive with oxygen). Hydrogen is always +1 with nonmentals, -1 with metals. Oxygen is usually -2, -1 in peroxide. F is always -1.