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General Chemistry

Learn the toughest concepts covered in Chemistry with step-by-step video tutorials and practice problems by world-class tutors

3. Chemical Reactions

Polyatomic Ions

Polyatomic Ions are groups of multiple elements that possess a charge.

Polyatomic Ions
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Polyatomic Ions

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Polly Atomic ions represent tightly bound groups made of different elements that possess in overall charge. That charge can be either positive or negative. For now, we're gonna focus on Lee on the negatively charged once. So we're gonna take a look at our Polly, Atomic, oxy and ions. These are the negatively charged Polly atomic ions that end with oxygen. And when it comes to these poly atomic occean ions, weaken. Describe them as either being try oxides or tetra oxides. Let's focus on the try oxides. First, let's focus on the fact that it's has a letter T. If we look at this portion of the periodic table, we're going to say that these foreign blue represent possible try oxides, and they also form the letter T. Now the try oxides themselves, we say when their name ends with eight, they possess three oxygen's. So again, use this to help you reinforce this. Try oxides with tea when they end. With eight, they have three oxygen's. They form the letter T on the periodic table, so they all have three oxygen. So that's B 03 C 03 n 03 and s i 03 Then we have our Tetra oxides tetra. Some of you may know what that stands for Tetra oxides when their name ends with eight they possess for oxygen's because Tetra standing for four and those are represented by phosphorous and sulfur so they would have four oxygen's soapy 04 and s Alright, we've said Oxy and Ion, So we talked about a negative charge, but we don't see it quite yet. Click on to the next video and let's take a look when we start incorporating charges with these, try oxides and tetra oxides.
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Polyatomic Ions

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up to this point. We know how Maney Oxygen's are found within our tri oxides and tetra oxides. Now it's time to take a look at how do we determine their charges? We know that our try oxides are here within this T, and we know that they're called Try oxides because they have three oxygen's to them to think about their charges. There's a pattern when we take a look at the periodic table. So starting with Group Three A, we have minus three. So this would be B 033 minus or minus three. Then we go minus two minus one. So if minus two, all those in group four a would be to minus and then you know, three would be minus one. So here we determine the charges for the try oxides when they end with the name eight, we'll get to that later on with the trust rock sides the tetroxide here, we're going to start over again. So minus three minus two minus one. So minus three year four peel minus. We determined that they have four oxygen's because their teacher oxides and this would be s to minus notice. Here we have another slot here from minus one, which represents elements within this group. Seven A. We'll talk about them later on. So at this point, we determine who are try. Oxides are and who are tetroxide Czar, how maney oxygen's they have and what their charges are. Now that we've taken a look at these different types of Polly Atomic ions, let's continue onward and take a look at additional one.
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Polyatomic Ions

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with our try oxides and tetroxide. We determine the number of oxygen's and the charges associated with them. Now let's associate those structures with names with our try oxides. We have bore raped. So bore rate would tell us that we're dealing with boron so that b b 03 three minus carbonate carbon. So that's the CO three to minus that we discovered nitrate is dealing with the nitrogen. So no three minus one and then Cilic eight Must be the silicon that we have Here s I So s I 03 to minus. So this is their full Polly Atomic ion form with the name associated with it. Now let's look at our tetra oxides. So with our tetroxide, we have phosphate which must be dealing with our phosphorus. So that is P 043 minus. And then finally sulfate, which deals with our sulfur asshole for two minus. Now these represent our most common types off Polly atomic oxygen ions. And it's important to remember them as try oxides and tetroxide because from here we can slightly change their structures and introduce ourselves to new Polly atomic ions and with them new names. So click on the next video. Let's take a look at some of the situation
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Polyatomic Ions

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we now know the most common try oxides and tetra oxides. But what happens when we start messing around with the number of oxygen's they possess? Well, this is going to open up a whole new avenue of other policy, Tomic ions were going to say here, decreasing the number of oxygen's by one changes the ending to fight while keeping the overall charge the same. So up above We saw that a common tetroxide was sulfate. It's a tetroxide because it has four oxygen's and we knew that based on where it's located on the periodic table, it's charges to minus. Now in this form, it's ending. Is eight now going to decrease the number of oxygen's by just one? It becomes eso three. The overall charge stays the same. So it's two minus R eight ending now changes toe right, so s 03 to minus is solved. Fight. So right now, Yeah, So that is the difference in these poly atomic ions. So just remember, once we start manipulating the number of oxygen's, we can create a whole new Polly Atomic ion and a name associated with it. Now that we've seen this example, let's move on and look at some other Polly atomic ion
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example

Polyatomic Ions Example 1

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in this example question. It says, give the formal or systematic name for the following Polly Atomic ion P 033 minus. All right, so it has phosphorus within it. Looking back up, you know, that phosphorus was one of our tetra oxides and it came in the form of peel 43 minus its name was Foss Fate. We just learned that if I decrease the number of oxygen's by just one oxygen, it will give me a new Polly Atomic ion. So reducing it by one oxygen gives me this peel 33 minus. And remember, what that does is it changes the eight ending toe. Right? So this would represent our Foss fight ion. So it all hinges on the fact that you remember your try oxides and your tetra oxides. And then from there, changing the number of oxygen changes the ending of your Polly Atomic ion
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Problem

Give the systematic name for the following polyatomic ion.

NO2

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Problem

Give the systematic name for the following polyatomic ion.

CO22–

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Problem

Give the systematic name for the following polyatomic ion.

AsO42–

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Problem

The formula for the sulfate ion, SO42–. If the term of “thio” means the replacement of an oxygen by a sulfur, what is the formula for the thiosulfate ion?

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Polyatomic Ions

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Now let's take a look at the halogen oxygen ions. So these air Polly atomic ions, which still contain oxygen. But now our containing halogen, it's remember your halogen are the elements that are in Group seven a or group 17 of the periodic table they're referred to as also Oxy intelligence. Besides being called your halogen occean ions now, some key things to keep in mind when dealing with these types of Polly Atomic Islands. First of all, they're based name. The base name is just the beginning of the non metals name that is unchanged. The nonmetal here we're talking about is the halogen. The number of oxygen's in these polytechnic ions affect either the prefix, which is the beginning of the name and or Suffolk's, which is the end of the name we're gonna say here all the halogen occean ions possess a minus one charge, so that's what they all have in common. So let's take a look at our challenges. We have flooring, chlorine, bromine and iodine. The base name is just the beginning of their names. Flooring would be floor for its base name. Chlorine will be chlor for its based name. Brohm would be brome bro Me will be brome for its base name Now to this space. Then we can add unending, which we'll talk about next. I a dying is just I owed as its base Nate. Now we said that the number of oxygen's can affect both the beginning and or end of the name. If it has four Oxygen's, it uses the base name of Per and the Suffolk's ending off. Eight. So let's say we're looking at Let's Talk about bro. Me. So, bro me. BR has four oxygen's. They all possess a minus one charge. So the name of this would be per insert the base name in the middle per bromate. If they have 32 and one oxygen's, we're going to see how the name changes. So here, let's say we have Cielo three minus. So here, the beginning of the name, the prefix drops per no longer exist, but the ending of eight is still around because we're using chlorine. We use the base name of Chlor, so this would be Chlor eight. Next, let's look at I minus. So this would be I owe dint ending changes from eight toe ICT as you can see. And then let's say we have f o minus. So that would be hypo for the beginning of the name, the prefix and then floor aight. So just see, when we have four oxygen, we have the prefix of per when we have one oxygen, we have the prefix of hypo. When we have three or four oxygen's, we have the ending of eight. But once we drop down to two and won the ending changes to right. So these are things that you need to keep in mind when naming these different types of Polly atomic ions or, in this case, your oxy halogen or your halogen Occean islands. Okay, so the number off oxygen's determine the beginning and end of the name. Also the type of how do you use determines the base name.
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example

Polyatomic Ions Example 2

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in this example question it says named each of the following compounds. So for a we have scale of four minus and for B, we have b r O to minus. All right. Remember, we just learned that if your halogen oxy an ion has four oxygen's in it, it's gonna have those prefix of per because it is a chlorine. We're going to use its base thing, which is chlor. And because it has four Oxygen's, it's Suffolk's name is eight. Remember, all of these halogen oxygen ions possess a charge of minus one, so Cielo four minus is called per chlorate. This would be the per chlorate ion. Now let's do be for being. We have B R O to minus when we have to Oxygen's. We're going to say that there is no prefix because it is a br bro. Mean we're gonna use the base name of Brome and then remember, when we have to Oxygen's, we use the Suffolk's off, right? Okay, so bureau to minus would be the bro might ion. So these would be the two names for these halogen occean ions. Just remember, it's based on the number of oxygen's that they possess, which will affect both their prefix ed or Suffolk's names
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concept

Polyatomic Ions

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up to this point, We just examined Polly Atomic ions that possess a negative charge. Now it's time to look at the positively charged ones. We're gonna say most policy atomic ions are negatively charged except for NH four plus ion and H G 22 plus ion. We're gonna say NH four positive is called the ammonium ammonium ion. And it's gonna be the only major Polly Atomic ion that you're going to need to know that has a plus one charge. Then we're going to say we have a G 22 plus and know that little two is not a typo what this is. It's to individual h g plus one Mercury ions. They combined together. So now there's two of them together and they're combined. Charge comes out to two plus because each one possesses a plus one charge. We're going to say this is called Mercury one ion. Yes, I know it's a little might be a little bit confusing because the charges two plus, but realize that that two plus comes from the fact that each mercury is plus one. Alright, So again, a vast majority of Polly atomic ions you're going to encounter possess a negative charge these to possess positive charges
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concept

Polyatomic Ions

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now the other Polly Atomic ions don't fit into predictable patterns and still must be memorized. So we're gonna start out first with the other Tetra oxides. Now, these are called the others because they don't quite fit in with the other two major tetra oxides we've covered in sulfate and phosphate. Now permanganate per magnates formula is mn 04 minus one. Then we have chrome eight, which is C R 04 to minus and then finally aqsa late, which is C 204 to minus. Now remember, they're all tetroxide because they all possess for oxygen's. But we call them the others because we have magnesium, chromium and carbon. These elements are in different places on the periodic table, so it's hard to form a real pattern with them. Then we have the other Polly atomic ions. We don't really classify them as try oxides or tetroxide because some of them don't possess that many oxygen's or any oxygen's at all. So here we have cyanide. Cyanide is CN minus. We have hydroxide, which is O H minus peroxide, which is 02 to minus. So kind of reminds us a little bit of mercury one eye on where we have in this case to oxygen's. Each one is minus one so collectively there to minus. Then we have die Chrome eight, which is a little bit similar to crow, mate. So die, meaning that we kind of double things a little bit. But here it's cr 207 to minus instead of 08 Then we have Sion eight, which is related to cyanide. Sion eight is C N Oh minus. And actually it's Oh CN minus the correct way to write it. So cyanide doesn't possess an oxygen sign. It does possess an oxygen. Then finally we have acetate ion acetate is written as C two h 30 to minus. Now this will be the predominant form that you will see but later on in chemistry may see them showing in another form. You may also see it as C H three C o minus, So just keep your eyes open. When you see either form, both of them represent the acetate ion
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example

Polyatomic Ions Example 3

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So here. If we take a look at this example, it says based on your understanding of the poly atomic oxygen ions provide the structure for the bio sign aid Ion. All right, so we know that our sign eight ion is oh, CN minus. And remember, we've come across this prefix of Thile before. Remember, when we have this prefix of thigh Oh, it means that we're going to replace an oxygen with a sulfur. So if we're dealing with a Iot Sion eight, that means we're gonna replace one oxygen with a sulfur. In this case, we only have one oxygen. So it's just gonna get replaced with a sulfur. So this becomes s and in the rest of it stays the same S c N minus. So are signing it is one of our other Polly atomic ions of O. C. And minus. That was the key to knowing what Theo sign. It looks like. Remember, Theo just means replaced an oxygen. What a sulfur, while maintaining everything else about the poly atomic ion. The same. So our answer would be S C n negative
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Problem

Give the systematic name for the following polyatomic ion.

FO

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Problem

Give the systematic name for the following polyatomic ion.

IO3

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Problem

The silicate ion is the silicon version of the carbonate ion. Based on this description, provide the structure of the silicate ion.

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