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### Oxidation number?

Posted: Sun Mar 03, 2019 4:33 pm
Professor Lavelle briefly mentioned in lecture about knowing the oxidation number based on an element's location on the periodic table? What was he referring to? I never learned that in high school.

### Re: Oxidation number?

Posted: Sun Mar 03, 2019 4:43 pm
There are some rules that are helpful to identify an elements oxidations number, based on there location in the periodic table. For example, if the element is in group 1, its oxidation number is always +1. Likewise, if it is in group 2, the oxidation number is always +2.

### Re: Oxidation number?

Posted: Sun Mar 03, 2019 5:43 pm
Group 1 elements have +1. Group 2 elements have +2. Group 17 have -1. Group 16 have -2. The others can vary a bit depending on the element and its state.

### Re: Oxidation number?

Posted: Tue Mar 05, 2019 9:33 pm
Usually, you can find the oxidation numbers of an element in a compound by using the oxidation numbers of the other elements present in that same compound. For example, in MnO4-, you know that the oxidation number of oxygen is -2. Using that information, you can find the oxidation state of the manganese.
There are other rules too, such as the location on the periodic table, with Group 1 having a +1 charge, Group 2 having a +2 charge, Group 16 having a -2 charge (with the exception of oxygen in a peroxide), and Group 17 having a -1 charge.

### Re: Oxidation number?

Posted: Sat Mar 09, 2019 9:43 pm
We always know that oxygen has a -2 charge and hydrogen always has a +1 charge. Regarding electrochemistry, this is important because if we are given a molecule like XO2H2 with no charge where X is an imaginary atom, we know that X must have an oxidation number of +2

### Re: Oxidation number?

Posted: Sat Mar 09, 2019 11:14 pm
Group 1 (alkali metals) elements will always have a +1 charge, Group 2 has a +2 charge, group 7 has a -1 charge.

### Re: Oxidation number?

Posted: Sun Mar 10, 2019 7:30 pm
I know there are some exceptions to this, but how do you know if an element in a particular atom has a different oxidation number than usual (the one indicated by position in the periodic table?

### Re: Oxidation number?

Posted: Mon Mar 11, 2019 5:09 pm
He is referring to the groups and their charges on the periodic table.

### Re: Oxidation number?

Posted: Mon Mar 11, 2019 5:51 pm
If you follow along the columns of the periodic table then you can see the pattern of oxidation numbers. (E.g. row 17 species oxidation # is -1)

### Re: Oxidation number?

Posted: Mon Mar 11, 2019 5:53 pm
It's basically the idea that the group that an element is found can give clues as to what its oxidation number if. Note, that this doesn't work for transition metals. Example: elements in group 1 have an oxidation number of +1 and elements in group 2 have an oxidation number of +2. Elements in the second to last group (halogens) have an oxidation number of -1.

### Re: Oxidation number?

Posted: Mon Mar 11, 2019 7:16 pm
This list really helped me determined oxidation numbers!

### Re: Oxidation number?

Posted: Mon Mar 11, 2019 8:36 pm
There are certain elements that have specific charges. You need to know these to properly balance the redox equation.

### Re: Oxidation number?

Posted: Mon Mar 11, 2019 11:03 pm
Once you get the hang of what oxidation numbers belong to certain elements, then you can use those to calculate the unknown oxidation numbers of other elements. To do this you must match the overall charge of the substance with the unknown element