YTread Logo
YTread Logo

Writing Ionic Formulas - Basic Introduction

Jun 05, 2021
In this video, we will focus on

writing

formulas

for

ionic

compounds. At first we'll go over some

basic

examples, then we'll cover examples containing polyatomic ions and even transition metals, so before we start we need to know. the charges of common ions elements in the first column of the periodic table such as hydrogen sodium potassium rubidium even lithium these metals form positive charges when they become ions elements in the second column such as magnesium calcium these ions generally form more two charges and then a a the right, has elements of group three, such as aluminum, gallium, in group 3a, these elements form positive charges 3 together with aluminum, it has elements such as carbon, silicon, germanium, we do not have to worry about the charges of these elements because they can vary and usually you won't see them very often in

ionic

compounds on their own, at least now the next group you should know about is nitrogen, phosphorus, these usually form three negative charges and then you have elements like oxygen and sulfur, which generally form ions with two negative charges and then you have halogens like fluoride, chloride, bromide and iodide, these ions form negative charges so make sure you are familiar with the charges of certain elements.
writing ionic formulas   basic introduction
Now let's say if we want to write the formula of an ionic compound like sodium chloride. What you want to do is write down the ions that are in this compound. The sodium we said has a charge plus one as an ion and the chloride has a charge minus one. If the charges are the same, if they are one to one, you can just write the ions together, these two ions will combine into this nacl compound and that's all you have to do to write the formula if the charges are the same now let's try With another example of calcium sulfide, it might be good to have a newspaper table in front of you.
writing ionic formulas   basic introduction

More Interesting Facts About,

writing ionic formulas basic introduction...

You can go to Google Images and print one out and you want to have it next to you where you can see what the charges are. The calcium is in the second column of the table. The ion that will form a charge of two plus the sulfide is in group six to or group sixteen and those elements generally form charges of negative two, so because the charges are the same, even if the sign is different, these two ions will combine into one. -to-one ratio, so it will be cas calcium sulfide, let's try one more example, aluminum nitride, aluminum is in group 3a or group 13 of the periodic table, so it will have a charge plus 3 , nitrogen is in 5a or group 5a and has a charge of minus 3, so because they both have the same magnitude of charge, so to speak, we can write them in a one to one ratio.
writing ionic formulas   basic introduction
Now, what should we do if the magnitude of the loads is different? is not the same, so consider the example lithium oxide lithium is found in the first column of the periodic table, it is an alkali metal and has a charge plus one. Rust is a calcagen, it is in group 6a so it has a negative charge 2, so what does it do? what we do in this case, if the charges are different, you can use a cross-link method where the charge will become a subscript, so the lithium charge will become the oxygen subscript and the oxygen charge will become the subscript lithium and you could ignore any negative charges because the subscripts will always be positive, so the formula will be li 2 or one.
writing ionic formulas   basic introduction
Now you don't really need to write the one, so we can just leave it as li2o if there isn't a number, it's always supposed to be. one, that's why we don't need it, this is the formula for lithium oxide, that's what you need to do to write it down, so for practice, let's try another example of gallium bromide, so feel free to pause the video and prove. this example yourself, so what do you think the formula for this compound will be? So let's find the charge on each element, gallium, since one ion will form a charge plus three or three more, bromide will have a negative charge, so use the cross-link method it will be ga1 br3, so we could ignore that and leave it as ga br3, so that's the formula for gallium bromide.
Consider this ionic compound magnesium phosphide. Go ahead and write the formula for this ionic compound, so let's start with magnesium and magnesium. It is found in group 2a of the periodic table, it is an alkaline earth metal, so it has a charge plus 2. Phosphide is in group 5a, just like nitrogen, so it will have a negative charge 3, so which if you use the crisscross method it will be mg3 p2. and as you can see, it is not very difficult to write the

formulas

for ionic compounds. Before moving on to examples containing polyatomic ions, you need to know what the polyatomic ions are in your formulas. no3 less is nitrate, that is, with an ate no2 less is is called nitrite with a ito, so these are polyatomic ions, they are ions that contain many atoms, this is nitride, nitrite is a monatomic ion, it is an ion that consists of an atom, notice that if it is monotonic it has the ending in ide, but if you see eight or Usually, that represents a polyatomic ion po4 three minus, what is the name of this polyatomic ion?
Also go ahead and name these too po4 three minus is called phosphates with an ate po3 3 minus is phosphite and p3 minus is phosphide so p3 minus contains a single atom so it is a monatomic ion and therefore It has the ending in ide. Note that eight generally has one more oxygen than me. Now, what are the formulas for the following sulfate, sulfite and sulfur ions? sulfate is tan4 two minus so fight tan3 two minus and sulfide is s two minus try this, let's say if you have perchlorate chlorate chlorite hypochlorite and finally chloride what are the formulas for these ions? perchlorate is clo4 minus chlorate is clo3-1 chlorite is clo2 -1 and hypochlorite is clo minus chloride does not have any oxygen atom it is simply cl with a negative charge now what are the names of these ions or h minus or h minus is known like hydroxide cn minus is cyanide c2h3o2 minus is acetate this is oxalate co32 minus is carbonate hco3 minus is bicarbonate or hydrogen carbonate cro42 minus that's chromate and this is dichromate nh4 plus is ammonium and mno4 minus is permanganate so those are some other ions which you should also know so now let's go over some examples of how we can write the formula for potassium sulfate so that potassium is an alkaline The metal that has a sulfate charge plus one is a polyatomic ion which is tan4 two minus, you simply need to know which, unless your teacher gives you a polyatomic ion sheet, you must memorize this, so now the one will move to the right, the 2 will move to the left, so it will be k2 so4 multiplied by 1, for which we don't really need to write the 1, so we can leave it as k2 k2so4, so this is the formula for potassium sulfate, try this strontium.
Strontium phosphate is a group two alkaline earth metal and has a charge of plus two. This is something you should know, it's po4 three minus so the two will move here and the three will go there so it will be sr3 po4 two whenever you have multiple polyatomic ions you need to enclose them in parentheses try this barium nitrate , as well as strontium, barium is also a group two alkaline earth metal, so it will have the same charge plus two nitrates is no3 minus one, so using the cross-link method it will be ba1 no3 multiplied by 2.
As long as you have multiple polyatomic ions, be sure to enclose it in parentheses. Now we don't really need one so we can simplify it to ba and o32 so that's the formula for barium nitrate now let's try some other examples with transition metals, many transition metals contain varying charges for example the metal iron can be in the plus two oxidation state or in the plus three oxidation state, copper, for example, has two common charges plus one and plus two, so when Si is given the name of an ionic compound that contains a transition metal, you will see a Roman numeral, for example, let's say if we want to write the formula for iron sulfide 2, the Roman numeral tells you what the charge is, so you should know what it represents if you see this this represents a one this symbol represents two this represents three if you see a v v represents five if you see an i let's say to the left of the v it represents four now if you see the i to the right of the v you have to add instead of subtract so it's like five plus one, that's six, so what do you think this represents a v with two eyes on the right, so it's five plus two, that's seven?
So, you need to know or be familiar with Roman. number system then we have iron sulfide two, which means that the iron ion has a charge plus two. We know that sulfur has a charge minus two because both ions have the same magnitude of charge, we can simply write it in a ratio of one to one. it's just fes, but even if you used the crisscross method you would get fe2s2. Note that both numbers are reducible. We can divide both numbers by a common number, so it will become fe1 s1, which we can write like this.
Try it. this is sulfide rn3 so this time the iron has a charge plus three instead of a charge plus two and the sulfide is the same so the shape will be fe2 s3 so the roman numeral just tells you the charge of the element, let's try another example. this is copper to nitrite, so copper has a charge plus two as specified by the roman numeral nitrite, you simply need to know that it is the number 2 with a negative charge, so using the crisscross method it will be cu 1, but not you need to write the one multiplied by no2 with a 2 and that is the answer for copper nitrate 2 here is another copper phosphite 1, try that so that the copper has a charge plus one.
Phosphite is po3 with a negative charge three, so this will be cu3 po3 multiplied by one. since we have one next to po3, we don't need a parentheses for this example, so here's the answer: copper, a phosphite, try this one, vanadium, five dichromates, so vanadium can have a five dichromate oxidation state So that's vanadium five dichromate, go ahead and try this challenge problem, lead 4 oxide this This will be the last example for today, so lead has a charge plus 4 and oxide has a negative charge two, so using the cross-link method we will see that we will have a formula that is pb2 o4, but notice that two and four are even numbers, which means we can reduce it by two and should.
If you get into a situation like this, make sure you scale it back. If we divide it by two, we will get pb1 o2, which means that the final answer is simply pbo2, so if you can make sure that you reduce these subscripts until you get the lowest integer ratio and that's it for this video, thanks for watching and have a great day.

If you have any copyright issue, please Contact