Calculate Oxidation Numbers

Now the oxidation number is an important idea as we make our way towards oxidation and reduction reactions, otherwise known as redox reactions. Now, first, we're gonna say that the oxidation number itself is an elements ability to gain, lose or share electrons when alone or in a compound. And we're gonna say when it comes to oxidation numbers, it's important to talk about the natural state of an element now for Adam in its natural state. Also called It's Standard State. It's oxidation number or oxidation. State is equal to zero. Now remember, we have our periodic table here. We know that with our periodic table there are charges that are unique to different groups, and we know that certain elements exist in certain forms in nature. Now, when it comes to Group One A. We know that the charges plus one group too, is plus two three years plus three. Anyway, we tend to foray. We tend to skip because some elements have varying positive charges. So we're just gonna skip that. We know that Group five a is minus three, minus two minus one. And remember, everything is trying to become a noble gas. They're perfect. So they tend not to have charges. If you don't remember this or you haven't seen my videos on it and you want to explore this a little bit further, make sure you take a look at my videos on periodic table charges. Now, also, remember, we've talked about natural states of elements in the past as well. So when it comes to elements of the periodic table, we have our die atomic molecules. Those are hydrogen, which is H two nitrogen, oxygen flooring, chlorine bro. Mean and, of course, our ideye. Also remember that phosphorus tends to exist as P four in its natural state when found in nature, and that sulfur is s eight. And since selenium is right below sulfur, it is s e eight. These are the natural forms of these different elements when they're found in nature and remember all the others. I'm not writing them in because in nature they exist as mono atomic atoms. This you can also remember refresh your memory by taking a look at my periodic table videos. We talk about the natural state of elements, but right now, just realize that if you find an atom in its elemental state or natural state of Standard State. Whatever term you're most comfortable with, its oxidation number will be equal to zero.

in this example question. It says which of the following compounds would have an oxidation number, or oxidation state equal to zero? So remember when an Element or Adam is found in its standard or natural state, it's oxidation number or oxidation. State is equal to zero. So if we take a look here, we have sodium to begin with. A any remember exists as a mono atomic element in nature. It's natural form is just n a. So this would not be equal to zero. Next we have chlorine. Chlorine exists as a die atomic molecule. Exists naturally. SCL, too. So this is a helium, one of our noble gasses. All the noble gasses art, mono, atomic, meaning they exist by themselves in nature. So this is the natural state of helium, and therefore it's oxidation number or oxidation. State would be equal to zero. So this is our answer. But let's look at the last one. The last one is mag unease, and they're saying it's four. Mag unease is one of many elements that exists as mono atomic elements in nature. So it's natural state is just mn, so this would not work so out of all the choices, only Option C would have an oxidation number of zero

Now, when an element gains a charge, it's no longer in its standard or natural state, so it's oxidation will no longer be equal to zero now, ions recall, and ion is an element or compound with a positive or negative charge. Remember your positive ions air called cat ions and your negative ions are called your and ions. Now, for a mono atomic ion, the oxidation number is equal to its charge. So if they gave us, for example, the aluminum Ion Aluminums and Group three Years, so it's charges three. Plus, If we see a charge present for that Monaco for that element, that is also it's oxidation number. Okay, but remember, it has to be in its eye on form for the charge and oxidation Number two equal one another. Okay, that's not always going to be the case we're going to see later on. They're gonna be cases where, ah, particular element, it's oxidation. Number can range widely based on what it's connected to. But for right now, if you see an eye on you, see its charge. That charge is equal to its oxidation number, so keep that in mind as we click on the next video and attempt an example. Question

So here it says which of the following elements would have the most positive oxidation number based on its Ionic. For now, if you've watched my videos on periodic table charges, you'll remember that the periodic table has some key things we need to remember when it comes to particular elements and their charges. For example, Silver Silver's a transition metal. Most transition metals have multiple charges. Silver, on the other hand, does not remember. Silver is always plus one for its oxidation number. Scan Diem Skandia is also a transition metal. It's in Group three b. Remember so Group three B elements. They tend to have a charge off plus three. Next we have sodium. It's in Group one A. So it's charge is plus one, and then sulfur is in Group six. A. So it's charge is minus two. We're looking for the most positive oxidation number, and that would have to mean that Option B is the correct choice. It has the biggest positive value of plus three. Remember, if you haven't gotten a chance to look at my periodic table videos on charges, and you just wanna go and take a look at the different types of elements and their charges. I highly suggest that you go back and take a look, because when it comes to charges of elements, it's gonna form a foundation for a lot of later topics we're going to cover in chemistry one in chemistry, too. All right, so just remember, in this question, the answer would have to be option be. It has the most positive charge and therefore the most positive oxidation of

Like we said before, oxidation numbers don't always correspond to real charges, and therefore a list of rules will be necessary. Now we're going to say when different elements are in a compound, these specific rules will be used to calculate our oxidation numbers. Now here, let's take a look at these specific oxidation number rules. When it comes to Group One elements, they will be plus one when connected to any other element. So that's something similar to charges of groups, and we're gonna see some similarities between oxidation numbers and charges. But then we're going to see a huge deviation from that group. Two A plus two. When they're connected to another element flooring, it's minus one. When it's connected, toe any other element. Now this is where things start to change. Hydrogen can be either plus one or minus one. It's plus one when it's connected to non metals, for example, if hydrogen is connected to glory or hydrogen is connected to oxygen or it's connected to the nonmetal of nitrogen. In all these instances, since hydrogen hydrogen is connected to a non metal, it's oxidation number. We plus one. Now it's negative one. When it's connected toe a metal or borrowing So, for example, and a H or C H two or B H three. In these cases, hydrogen will be minus one for its oxidation number. Now oxygen is even Mawr varied. We're going to say here that oxygen, when it's not a peroxide or super oxide, it's oxidation numbers minus two. When it's in its peroxide form, it's oxidation. Number will be minus one. Now. What exactly is a peroxide? Well, a peroxide, we're going to say, is when you have to Group one elements connected to two Oxygen's So example h Two Hydrogen, which are in Group one egg to oxygen's. This would be hydrogen peroxide ally 202 lithium peroxide or K 202 Potassium peroxide. Now, if oxygen is a super oxide, it's oxidation. Number is minus a half. What is a super oxide? Ah, super oxide is when you have one Group one a element with two oxygen's. So here we could have potassium super oxide CSE, um, super oxide, sodium super oxides. So just remember oxygen. Very soap. Just look be on the lookout. Do you have a super oxide or peroxide? If not it's oxidation. Number is minus two. And then finally, when we're talking about groups seven and we're talking about chlorine, bromine and iodine, they're going to be minus one except when they're connected to oxygen. In that case, we won't know what their new oxidation number will be and will have to calculate it. So again, we use these specific oxidation number roles when we're talking about different elements connected together. So we're gonna have to utilize them to determine the oxidation number of any element given to us within a compound.

here. In this example, it says which compound has oxygen with lowest oxidation state? If we take a look at the first one, we have n a 02 We have one group on a element with two oxygen's. Remember, that pattern tells us we have a super oxide, and if you have a super oxide, that means the oxidation number of oxygen is minus a half for the next one. We have CO two now. It's not a super oxide. For to be a super oxide, we would need one group one a element with the two. Oxygen's carbon is not in Group One A. It's a group for a so it's not a super oxide. Next, it's not a peroxide, either. To be a peroxide, you need to group one elements with two oxygen's, so it's not a peroxide. It's not a super oxide. Therefore, oxidation number is minus two. For the next one, we have CS 202 That's two Sessoms, which are Group one A with two oxygen's that fits the definition of a peroxide. So this is a session peroxide, so with oxidation, number for oxygen would be minus one. And then finally we have 02 This is the standard or natural state of oxygen. Remember, an element found in its standard or natural state has an oxidation number of zero. So out of all our choice is the one that has the lowest oxidation number. The one with the most negative value would be be CO two. So just remember, if we have specific rules for that given element, utilize them to find the correct answer.

now, when asked to determine the oxidation number of a non listed element within a compound, we're gonna follow the next four steps. Now, remember, we've gone over the specific oxidation number rules for certain elements. This applies to elements that are not found within that list. So step one, you're gonna treat the non listed element as X You're gonna right. You're gonna use the list to write the known oxidation number off other elements within that compound. For example, if you see oxygen is in that compound and it's not a peroxide or super oxide, we know it's oxidation. Number would therefore be minus two. Step three. If Element has a sub script, then remember to distribute it and then step four. Add up the oxidation numbers, create an equation and make it equal to the charge off the compound. So these are the rules that we're going to employ when looking for non listed elements within a compound, and we'll see how how we use utilize these four steps to get to our oxidation number for that particular element. Now that we've gone over them, click on the next video and let's take a look at an example question

here, It says, give the oxidation number of the carbon atoms in the acetate ion. All right, so we're gonna say we're looking for carbon, so carbon is going to be our X hydrogen, when it's with non metals is plus one and then oxygen here in It's not an ox, super oxide or peroxide. So it's minus two. So we have two carbons. Each one is X plus three hydrogen. Each one is plus one plus two oxygen's. Each one is minus two. This equation equals the charge of the ion, which is minus one. So all we have to do now solve for X so two X plus three minus four equals negative one two X minus one equals negative one. So add one to both sides here. So here, you know, weird turn of events. You can see that X now equals zero. So here the oxidation number off carbon within the structure is zero. So there are moments where you're oxidation number could be zero, and the element is not not not in its natural state, such as in this example. So again, the oxidation number of carbon when we calculated it comes out to be