Oxidation Number


Moderators: Chem_Mod, Chem_Admin

America Alvarado
Posts: 109
Joined: Sun Oct 04, 2020 12:15 am
Been upvoted: 1 time

Oxidation Number

Postby America Alvarado » Thu Nov 12, 2020 3:50 pm

How do you determine the oxidation number of a molecule? For example the oxidation number of ClO4-? Thank you

darchen3G
Posts: 110
Joined: Wed Sep 30, 2020 9:39 pm

Re: Oxidation Number

Postby darchen3G » Thu Nov 12, 2020 3:54 pm

Oxygen usually has a -2 oxidation number, and the molecule has an overall -1 charge.
Let x be the oxidation number of Cl.
x + 4(-2) = -1

In this case, Cl has an oxidation number of 7.

George Cazares 1E
Posts: 51
Joined: Wed Sep 30, 2020 9:39 pm
Been upvoted: 1 time

Re: Oxidation Number

Postby George Cazares 1E » Thu Nov 12, 2020 4:04 pm

To find the oxidation number of ClO4- you can use a simple equation. Assuming oxygen will have a (-2) oxidation number and knowing the total charge of the molecule is (-1) you can write the equation Cl+4(-2)=-1. Solving for Cl gets you Cl=7, which means the oxidation number for Cl is +7.

Gicelle Rubin 1E
Posts: 81
Joined: Fri Oct 02, 2020 12:16 am

Re: Oxidation Number

Postby Gicelle Rubin 1E » Thu Nov 12, 2020 4:54 pm

George Cazares 1E wrote:To find the oxidation number of ClO4- you can use a simple equation. Assuming oxygen will have a (-2) oxidation number and knowing the total charge of the molecule is (-1) you can write the equation Cl+4(-2)=-1. Solving for Cl gets you Cl=7, which means the oxidation number for Cl is +7.


I apologize if this is a silly question but how do you determine the oxidation number as you did with oxygen?

AmyHo2K
Posts: 99
Joined: Wed Sep 30, 2020 9:39 pm

Re: Oxidation Number

Postby AmyHo2K » Thu Nov 12, 2020 11:30 pm

Gicelle Rubin 1E wrote:
George Cazares 1E wrote:To find the oxidation number of ClO4- you can use a simple equation. Assuming oxygen will have a (-2) oxidation number and knowing the total charge of the molecule is (-1) you can write the equation Cl+4(-2)=-1. Solving for Cl gets you Cl=7, which means the oxidation number for Cl is +7.


I apologize if this is a silly question but how do you determine the oxidation number as you did with oxygen?


Oxygen normally have an oxidation number of 2 unless it's bonded to Fluorine.

Keerthana Sundar 1K
Posts: 98
Joined: Wed Sep 30, 2020 9:52 pm

Re: Oxidation Number

Postby Keerthana Sundar 1K » Fri Nov 13, 2020 9:56 pm

I apologize if this is a silly question but how do you determine the oxidation number as you did with oxygen?


When the oxygen is not bonded to another atom, we can determine the oxidation number as -2 because oxygen requires 2 electrons to be put in a stable form (full octet). When bonded, each oxygen atom will have the oxidation number of -2, and this is usually not flexible because of oxygen's high electronegativity and how it does not have a d subshell. In comparison, other elements such as Cl can have a different oxidation number because it isn't as electronegative and has a d subshell, so its oxidation number can vary more freely. Hopefully this helps!

Alessia Renna 1D
Posts: 51
Joined: Wed Sep 30, 2020 9:36 pm

Re: Oxidation Number

Postby Alessia Renna 1D » Sat Nov 14, 2020 12:41 pm

Because ClO4- has a charge, the oxidation numbers of each element in the compound must add up to equal the charge. We know that oxygen has an oxidation number of -2, and there are 4 Oxygens in ClO4- so O = -8. Because the charge is -1, we know that Cl must be +7 becuase 7 + -8 = -1

SophiaNguyen_2L
Posts: 105
Joined: Wed Sep 30, 2020 9:59 pm

Re: Oxidation Number

Postby SophiaNguyen_2L » Sat Nov 14, 2020 1:09 pm

All you'd have to do is set the charge of the atoms equal to the overall charge of the compound. So it'd be like:

4(O) + (Cl) = -1
4(-2) + (Cl) = -1
-8 + (Cl) = -1
Cl = +7

Andrew Yoon 3L
Posts: 93
Joined: Wed Sep 30, 2020 9:36 pm

Re: Oxidation Number

Postby Andrew Yoon 3L » Sun Nov 15, 2020 5:32 pm

To find the oxidation number of the example you gave, first you need to set up an equation. Since the final charge of the molecule is given (-1), we can set that equal to the charges of the Cl and O. -1 = (Cl) + 4(O). For O, we can assume it has a -2 charge. So then, we can solve the charge for Cl. -1 = (Cl) + 4(-2) --> Cl = -1 + 8 --> Cl = +7.

America Alvarado
Posts: 109
Joined: Sun Oct 04, 2020 12:15 am
Been upvoted: 1 time

Re: Oxidation Number

Postby America Alvarado » Thu Nov 19, 2020 12:54 am

So are the oxidation numbers usually given? or are we suppose to know that Oxygen has an oxidation number of -2?

Massimo_Capozza_1G
Posts: 104
Joined: Wed Sep 30, 2020 9:52 pm

Re: Oxidation Number

Postby Massimo_Capozza_1G » Thu Nov 19, 2020 1:51 am

America Alvarado wrote:So are the oxidation numbers usually given? or are we suppose to know that Oxygen has an oxidation number of -2?


I am also confused about this. Will we be given the oxidation numbers, or do we have to memorize some of them?

605291562
Posts: 91
Joined: Wed Sep 30, 2020 10:07 pm

Re: Oxidation Number

Postby 605291562 » Sat Nov 21, 2020 4:14 pm

Hi! Posted above are great ways to find the oxidation number however for this course I don't think it is necessary to know. It is not listed in Professor Lavell's guidelines which I feel are an accurate way to know what is necessary to know.


Return to “Formal Charge and Oxidation Numbers”

Who is online

Users browsing this forum: No registered users and 1 guest