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0:01
so in this lesson today we're going to focus on chemistry so for those of you who are about to learn chemistry or about to take a chemistry course this video will be very useful for you so the first thing we need to talk about is the periodic table now I recommend that you go to Google images and type in periodic table and print one uh that you could find but the first thing you need to know are the names of the elements so on the first column on the left which is group one you have H which
0:40
stands for hydrogen Li which stands for lithium na which stands for sodium K is potassium RB Is Rubidium CS cesium now it's important to know that the elements in group one when they form ions they tend to form ions with a positive one charge so just keep that in mind now oh by the way the metals in this group like not hydrogen but lithium sodium pottassium rubidium and cesium these metals are known as the alkalite metals you need to know that name as well now in group two you have elements
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such as burum be and then mg which stands for magnesium and then CA calcium Sr strum ba a barium now these elements are called the alkaline earth metals and as an ion they form a positive two charge the elements in group one they have one valence electron the elements in group two contain two valence electrons and when they give those two valence electrons away they tend to form ions with a positive two charge sometimes you'll see it written like this 2+ instead of positive
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two now towards the right we have other elements like Boron aluminum gallium indium thalium and so forth so this is Group 13 which is also called uh group 3A in the periodic table elements like aluminum gallium and indium they can form positive three charges next we have group four which contain elements like carbon silicon geranium tin lead and so forth elements like germanium tin and lead they could form positive two and sometimes positive four charges so some ions can have multiple
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oxidation States or charges now to the right of carbon you have elements in group 5A or group 15 so these include nitrogen phosphorus arsenic antimony and bismuth nitrogen and phosphorous they typically like to form negative charges particularly a negative3 charge and group 6A you have elements like oxygen sulfur selenium te tonium and then uh P these elements like to form Nega -2 charges they're known as the cogens and then in group 7A you have the halogens
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like Florine chlorine bromine and iodine they like to form negative one charges so so in group 5A these elements have five valence electrons in group 6A these have six valence electrons in group 7A these elements have seven veence electrons the valence electrons are basically the electrons in the outermost energy level which we'll talk more about that later now in group 8 a you have elements like helium and then neon argon Krypton Xenon and so forth helium is above neon so I didn't really
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write it but the noble gases you need to know that they're chemically inert they're very stable so for the most part they generally do not participate in chemical reactions so they're highly stable the halogens are extremely reactive and so are the alkaline metals in group 1 a now from group 3 to 12 you have the transition metals and I'm not going to go through all of them just a few common ones such as TI that's titanium CR is chromium MN is manganese Fe is iron Co
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is Cobalt ni I is nickel CU U is copper ZN is zinc and then AG is silver CD is cadmium HG is mercury Au is Gold PT is Platinum PD Palladium and those are the most common ones you'll see now the inner transition metals which is below the transition metals they're called um you have the lanthanide and the anide series the most common ones that you'll probably see are thorium th and uh uranium the other ones you'll rarely hear about them in a typical chemistry course but these two
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you might be tested on the name of these elements so make sure you know those two I remember on my first day when I was in my AP Chemistry class in high school that we were told we're having a pop quiz the next day on naming the elements of the periodic table and we had like 30 or 40 elements to name so make sure you know those names because chances are you'll probably have a pop quiz on that now the next thing we're going to talk about is distinguishing atoms from
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molecules so what is the difference between an atom and a
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molecule some elements are made up of atoms some are made up of molecules but what is the difference zinc for example is a metal that is composed of atoms hydrogen well not hydrogen but iron metal is composed of atoms carbon is atomic nature and so is aluminum now hydrogen is diatomic it's a molecule it's an individual particle that contains two atoms nitrogen is also a diatomic molecule it's a molecule that consists of two atoms so is Florine which exists
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as F2 there's oxygen gas O2 chlorine gas cl2 and then liquid bromine br2 and solid iodine I2 so these are all molecules now you need to distinguish an element versus a compound a Pure Element consists of one type of atom whereas a compound consist of different types of atoms so for example zinc is a Pure Element it's only composed of zinc atoms hydrogen gas is a Pure Element it only consists of hydrogen sodium chloride is a compound because it consists of two different
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types of atoms sodium atoms and chlorine atoms iron is a element because it consists of only one type of atom iron metal water is a compound because it consists of two different types of atoms hydrogen atoms and oxygen atoms and so that's how you could distinguish a compound versus a Pure Element pure elements can consist of atoms or they can consist of molecules now there's two types of compounds that you need to be able to distinguish and those are ionic compounds and molecular
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compounds so sodium chloride is an ionic compound carbon dioxide is a molecular compound sodium is a metal chlorine is a non-metal carbon is a non-metal and oxygen is a non-metal so typically ionic compounds are composed of metals and non-metals molecular compounds are typically made up of nonmetals bonded to each other but both of these are compounds because they consist of two or more different types of atoms metals tend to contain positively charged ions like cations
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nonmetals tend to form negatively charged ions also known as anions so ionic compounds they consist of ions now the metal nonmetal rule is it's not always the case so to speak but generally speaking if you see a compound with a metal and a non-metal it's going to be ionic so some other examples would be like magnesium oxide that's ionic or pottassium fluoride that's ionic however ammonium chloride is one of those rare exceptions it's ionic because it consists of ions however there's no
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metal in this compound nitrogen hydrogen and chlorine are considered non-metals and so this is one of those rare exceptions where you have an ionic compound that doesn't consist of a metal and a non-metal so at this point you might be wondering how can I determine which element is a metal or a nonmetal and you could use the periodic table to do that so if you have it with you you want to pull it out and look for the elements in group 13 starting with Boron and then aluminum and you want to
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focus on these elements silicon geranium and then arsenic antimony te and then over here will be like ponum and atine and you want to focus on this line that you see here some periodic tables will show this line others will not so the elements towards the left of this line they're Metals metals like to give away electrons and as we discussed before they like to form positively charged cations or ions to the right of that line you have the non-metals which like to acquire
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electrons and form negatively charge ions or anion now on this line you have metalloids for instance Boron for example is a metalloid a metaloid has properties in between that of a metal and a non-metal so metals they conduct electricity nonmetals do not they are insulators metalloids are in between they can conduct a small amount of electricity so the metalloids that you need to be aware of are Boron silicon geranium aluminum is a metal it conducts electricity very well arsenic antimony
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te these are metalloids but on a typical test the two metalloids that you really need to be familiar with are germanium and silicon those are the most common ones that you may have to know or that you'll be tested on but everything to the left of that are metals and to the right of that line are non-metals and so that's how you can easily tell if an element is a metal or non-metal you need to be familiar with the periodic table now I'm going to give you a mini
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quiz I'm going to write out a list of pure substances and I want you to characterize them as being made up of atoms or molecules or let's say if they're a pure element or a compound and if they're a compound what type of compound is it an ionic compound or a molecular compound so let's start with sulfur trioxide how would you describe it so first is this substance is it composed of atoms or molecules notice that it's made up of many different atoms so this is a
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molecule now because it's composed of different atoms it's not a Pure Element but rather it's a compound so this is called a molecular compound it's a compound that consists of molecules now what about let's say cl2 now this is composed of only one type of atom so it's a Pure Element now it consists of molecules not just atoms because we have multiple atoms a molecule can be made up of one type of atom or different atoms if it's one type of atom like what we see here
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then it's it's a Pure Element but if it's made up of different type of atoms it's a compound so this is a molecule as long as you have basically one unit or one particle that consist of two or more atoms whether those atoms be of the same type or of a different type it's a
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molecule now what about let's say magnesium magnesium is a metal and metals typically are composed of atoms and since we only have one type of atom it's a Pure Element and so that's all we can say about magnesium now what about sulfur which typically consists in the form of S8 or it's it looks like that s sulfur is actually made up of molecules
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so one sulfur unit has basically eight sulfur atoms connected in an octagonal shape like this and so that's one whole unit but it's a molecule because it's composed of multiple atoms now it's not a compound because it's only composed of one type of atom so this is a Pure Element
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now what about this one l i BR how would you characterize this substance so the fact that we have two different types of atoms lithium and bromine means that we do not have a Pure Element so rather this is a compound now compounds are composed of atoms or ions in this case this compound it's composed of ions lithium is a metal which is found on the left side of the periodic table bromine is a non-metal and that's found on the right side of the periodic table as we know lithium forms
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positively charged ions bromine forms negatively charged ions and so we have an ionic compound so this compound is not composed of atoms it's composed of ions now the video that you're currently watching is the first half of the entire video so for those of you who want to gain access to the second half of the video you could find it on my patreon page if you wish to support it now I do have some other video content on that page so feel free to take a look at that
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if you're interested in doing so now let's get back to this video now let's shift our Focus to naming compounds and let's start with molecular compounds because they are a lot easier to name so let's start with CO2 as an example now the first element that we have on the left which is C that's carbon the second element on the right with the symbol o represents oxygen but the second element will have the suffix i so instead of writing oxygen we're going to write
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oxide however we do have a subscrip next to O and it's a two if you don't see a number it's always assumed to be a one so CO2 is the same as c102 now you need to be familiar with these prefixes mono corresponds to One D corresponds to two Tri is associated with three and then Tetra is equivalent to four Penta represents five and then hexa is equal to 6 hepta represents 7 OCTA is equal to 8 Nana is N9 and deca is equal to 10 now we don't have to say monocarbon if there is a one or no
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number at all you can disregard the word mono for everything else you do have to use the prefix now this is true only for the first element for the second element you do have to use the prefix mono now we do have D because of the two so instead of saying carbon oxide we're going to say carbon
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dioxide now let's try these two examples Co and let's say n205 So Co that's going to be carbon and this time we have a one in front of the oxygen but carbon
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monoxide so for the second element if there's a one you do use the prefix now what about n205 how can we name that particular molecular compound so we know that two corresponds to D and five is Penta n is the chemical symbol for nitrogen and O is for oxygen so instead of saying nitrogen we're going to say d nitrogen and instead of saying Penta oxide we're going to take off the A and use the O so we're going to say pentoxide you don't want to put two vowels together now go ahead and try these two
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S cl6 and P br3 take a minute and work on those examples so s is the chemical symbol for sulfur CL is the chemical symbol for chlorine now there's six chlorine atoms in this molecular compound and six is associated with the prefix hexa so this is going to be sulfur hexa chloride make sure to to add the suffix IDE now what about PBR so p is the symbol for phosphorus BR is the symbol for Bromine but we're going to say bromide and we have a subscript of three so three is
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associated with tri so this is phosphorus Tri bromide at this point let's talk about how to name ionic compounds so let's start with Ki how can we name this compound K is the chemical symbol for potassium I is the symbol for iodine but when naming compounds instead of writing iodine or iodine we are going to take this off and replace it with I so it's going to be iodide and that's the name of this compound potassium iodide that's all you need to do now what about
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mgbr2 keep in mind the rules for naming ionic compounds differ from naming molecular compounds mg stands for magnesium BR is bromine but we're going to add the suffix i so the answer is magnesium bromide for ionic compounds you do not use the prefixes mono di Tri Tetra and so forth so there's no need to call this magnesium di bromide magnesium bromide will always be mgbr2 now go ahead and try these two examples write the names of these two ionic compounds so the first one CA stands for
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calcium and O is oxygen but we're going to to add the suffix i so the answer is calcium oxide for the next one Sr stands for strontium and F stands for Florine but we're going to write fluoride instead so this is strontium fluide now as you can see naming ionic compounds is not too difficult now you need to be familiar with something called polyatomic ion
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poly means many so these are ions that consist of multiple atoms so some common polyatomic ions would be S so42 minus which is called sulfate oh minus that's hydroxide nh4+ ammonium C2 h32 minus that's acetate let's see NO3 minus that's nitrate p43 minus phosphate CN minus cyanide M4 minus permanganate cr207 2us that's dichromate and there are some other ones but I have a video on polyatomic ions on YouTube you can feel free to check that out if you want a a more detailed list now I recommend
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memorizing the list that you see here because you're going to see these ions you're going to use them a lot in the rest of your Chemistry course so make sure to commit that to
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memory so let's say if we have the ionic compound na2so4 how can we name it well using the periodic table which you'll typically have access to on an exam you can see that na is sodium now so4 that is not on the periodic table you need to recognize that this is a polyatomic ion so once you know it's sulfate all you have to say is sodium sulfate and that's why it's important to commit these to memory so for example let's say if we want to write the name of K3 K stands for potassium and you simply
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need to know that NO3 represents nitrate so this is called pottassium nitrate go ahead and try these two examples Al O3 and let's say Li I C2 H3 O2 so Al stands for aluminum and O is a polyatomic ion known as hydroxide so this is simply called aluminum hydroxide now for the next one we know that Li represents lithium and C2 h302 is another polyatomic ion that you need to memorize and that's called acetate so this is lithium
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acetate now how would you name these two fe2 and fe3 be careful with these two examples now f Fe e we know as the chemical symbol for iron and cl is chlorine so we could say it's chloride and so this is going to be called iron chloride now that would be correct but there's more to it now these are actually two different ionic compounds and we can't use the prefix dantry so we can't use iron chloride to identify these two different substances we need to do something else
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now typically when you have a transition metal or some other non-transition metals that have multiple oxidation States or multiple charges like this element iron you need to use Roman numerals the first thing we need to do is determine the oxidation state or the charge on iron metal so let's focus on fe2 so we have one Fe particle and two chlorine particles what is the charge on chlorine chlorine likes to form a negative one charge so the total negative charges are -2 now
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this one Fe particle and so it has to have a positive two charge in order to neutralize the net Nega negative2 charge rather and so to name this it's going to be iron to Chloride because the oxidation state of iron met is pos2 in this particular compound so at this point you can guess what the name of fe3 is going to be so we have three chloride ions which means the total negative charge is minus 3 so this Fe atom has to have a total positive 3 charge and so since the oxidation state
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of iron metal is positive3 this is going to be called iron 3 chloride now for those of you who need to review Roman numerals I do have a video on that so if you were to type in Roman numerals organic chemistry tutor in YouTube it should come up if you need to review Roman
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numerals go ahead and try these two examples PBO and pb2 so let's start with PB o PB represents lead o is oxygen but we're going to write that as oxide now we need to determine the charge on lead we know the charge on oxygen is -2 and so the charge on lead is plus two so these numbers have to add up to zero we only have one oxygen ion and one lead ion so because we have one of each the charges have to have the same magnitude but the opposite sign so now that we have the oxidation state of
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lead we can write the name so this is called lead 2 oxide since it has a plus two charge now there's something I do want to mention when writing ions some teachers will want you to write the ion this way as opposed to this way so they may want you to write pb2+ instead of plus two and even in certain online homework assignments you may have to input it this way me technically I have the habit of writing ions like this sometimes you may see me write it this way too but in
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case I just naturally revert back to my old habits just keep in mind that you may have to write it this way if your teacher requires you to do so so I just want to put that out there now let's go back to this one pbo2 so what is the oxidation state of PB in this example a simple way to find the answer is to write an equation so we have one PB atom and two oxygen atoms I'm going to write as Ox so that you don't distinguish so you don't think of O as zero now the net charge of this compound
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is zero so we're going to set it equal to zero our goal is to solve for Pb now we know the charge in oxygen is -2 so 2 * -2 is4 and if you add four to both sides you'll see that the oxidation state of PB is four or if you do it the other way so we have one PB ion and two oxygen ions each with a -2 charge so the total negative charge is4 which means the total positive charge has to be +4 and so we have lead for oxide now what about this one cu2 so4 how can we name that particular
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ionic compound go ahead and try that so let's write an equation so we have two copper atoms now so4 you don't want to split that into separate atoms instead recognize it as one unit it's a polyatomic ion and the net charge has to be zero now we know the charge on the sulfate ion which is -2 and so if we add two to both sides we'll get 2 cuu is equal to pos2 and now let's divide both sides by two two ID two is one so the oxidation state on copper is positive
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one now let's confirm it with the other technique in this case we have two copper ions and one sulfate ion the charge on sulfate is min-2 so that's the total negative charge the total positive charge has to be plus two and when you divide that to the two copper atoms that we have here each of them has to have a plus one charge so that is the oxidation state of copper positive one so this is going to be called copper one
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sulfate now let's talk about writing formulas of compounds so let's say if let's start with molecular compounds let's say if I give you the name we'll go with phosphorus pentac chloride what is the chemical formula of this molecular compound now to write the formulas of molecular compounds it's pretty straightforward it's simply the reverse of what we've been doing before phosphorus is p and then we have chloride so CL and Penta tells us that we have five chlorine atoms so the answer is
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pcl5 now let's try a few other examples so what about
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sulfur tetrafluoride try that one sulfur is s and then we have Florine and Tetra tells us that we have four Florine atoms and so that's it for this example now let's try one more
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nitrogen monoxide so we have nitrogen and mono means one so we have only one oxygen and so NL is nitrogen monoxide now writing formulas for ionic compounds could be a little bit more challenging so let's start with something simple let's say pottassium
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bromide now if if you were to say it's KBR you would be correct now what about this one let's say if we have
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sodium actually let me use something different let's say aluminum
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sulfate how would you write the formula for that ionic compound now you might be thinking aluminum is Al sulfate is so4 so Al so4 if you do this way the answer will not be correct you need to make sure the charges of the ions are balanced aluminum has a positive three charge or you could write 3 plus if you want sulfate has a -2 charge or two minus charge now what we need is in order to make the total charges the same we need two aluminum ions which will give us a
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net charge of pos6 and three sulfate ions which will give us a net charge of6 and these two will cancel so it turns out that the formula is al2 so43 now whenever you have multiple polyatomic ions you need to enclose them within a parentheses now let's try some some other examples so let's say if we have pottassium
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phosphate what is the chemical formula for this compound so start by writing the ions pottassium has a positive one charge phosphate has a ne3 charge now a quick and simple method is to replace the numerical value of the charges with subscripts so this is going to be K3 P4 * 1 which we could simply leave it as P4 and using that technique you can quickly write the formula for the ionic compound so it's K3 P4 try this one calcium iodide feel free to pause the video now
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calcium is an alkaline earth metal it's found in group two so it's going to have a positive two charge iodide is a hogen in group 7A and those elements form negative 1 charges so if we switch the charges with subscripts it's going to be ca1 I2 but we don't need to write the one so it's simply CA I2 and that's the answer for that example now what if we have iron 2 sulfide not sulfate but sulfide sulfate is S so4 2 minus sulfide is different so what if we have this how can we write the
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formula if you see the Roman numeral it tells you the charge or the oxidation state on Fe which in this case is 2+ sulfide is simply which is a calogen in group 6A and those elements typically form a -2 charge as an ion now anytime you have two ions with the same charge you could simply write them together so the answer will be FES if you use this technique you're going to get fe2 S2 now if you have even numbers you can reduce it so you can divide the subscripts by two and that
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will give you fe1 S1 which is basically f s so anytime the charges are the same you could just simply write them together as FES now let's try this one aluminum phosphate so go ahead and take a minute and try that example so aluminum has a positive 3 or a 3 plus charge phosphate is p four with a 3 minus charge now because the charges are the same we can simply write them together so the answer is going to be Al P4 and that's it for this example now what about copper to phosphate what about this
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example so we have copper and and the Roman numeral 2 gives us its oxidation state and phosphate is still the same P4 3 minus now this time let's swap the charges and write them as subscripts so it's going to be cu3 and then P4 so we need to write this within a set of parentheses and then let's write the two as a subscript so this is going to be the answer so so anytime you have multiple polyatomic ions you need to write it within a set of parentheses try this one tin 4
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oxide tin is represented by the chemical symbol SN and we have a 4 plus charge oxide it's going to be O2 minus now the chares are different so if we swap them and write them as subscripts it's going to be sn2 04 now notice that even though the subscripts are not the same they're both even in a situation like this you want to reduce it so divide each subscript by two so it's going to be sn12 but we don't need to write the one so the final answer is going to be
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sn2 so that's the chemical formula of 104 oxide now here's the last one we're going to try
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vadium 5 let me do that again vadium 5 oxide so vadium has the chemical symbol V and it's going to have a positive five charge or five plus charge oxide will have a -2 charge and if we switch is going to be v25 and so now you know how to write the chemical formula of ionic compounds so now let's move on to our next topic now if you have access to a periodic table look for the chemical symbol n it has an atomic number of seven and an average atomic mass of
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14.01 sometimes this is referred to as the mass number when dealing with Isotopes but on a periodic table it is known as the average atomic mass because there are many isotopes of nitrogen and this is the atomic number but let's talk about Isotopes and we'll get back to average atomic mass now let's focus on the isotopes of carbon that is carbon 12 and carbon 13 these are the most common isotopes of carbon there are some other ones but carbon 14 is another version but let's
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focus on just these two so these two isotopes they share the same chemical reactivity they're essentially the same they are both atoms of carbon so in a chemical reaction they will behave the same way however they do have different nuclear properties because the structure or the makeup of the nucleus is different now when you look at Carbon on a periodic table it's going to look like this you're going to see the atomic number of six which is true for all isotopes of carbon and you'll see the
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average atomic mass so this mass is the average of all the masses of the isotopes of carbon including carbon 12 carbon 13 and carbon 14 now here's the question for you which of these three Isotopes is the most abundant isotope of carbon on Earth today well because the average atomic mass is closest to 12 carbon 12 is the most abundant isotope but now let's talk about
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it let's calculate the number of protons electrons and neutrons in these two atoms to calculate the number of protons it's always equal to the atomic number to calculate the number of neutrons which is found in the nucleus it's equal it's the difference between the mass number and the atomic number now the number of electrons is equal to the atomic number which is basically the number of protons minus the charge so atoms are electrically neutral they have no charge so for atoms the number of
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electrons and protons are the same for ions they have a charge so in the case of an ion the number of protons and electrons differ a positively charged ion has more protons than electrons a negatively charged ion has more electrons than protons protons are positively charged electrons are negatively charged and neutrons are
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neutral so in the case of carbon 12 which I'm going to write this like this it has a mass number of 12 and an atomic number of six this is the opposite in which you see in a periodic table so carbon 12 has six protons because that that's the atomic number the number of neutrons is the difference between 12 and 6 so that's going to be six neutrons and for an atom of carbon it's going to be six electrons now for carbon 13 sometimes you'll see it written this way so this is the atomic number and
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this is the mass number carbon 13 has six protons and the difference between the mass number and the atomic number 13 - 6 is 7 so it has seven neutrons and we don't have a charge so it's still six electrons so the difference between these two isotopes has to do with their mass number one is 12 one is 13 and the number of neutrons so make sure you understand that because that's a a common test question Isotopes have the same number of protons and they have the same atomic number
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but they differ in the number of neutrons and they have different Mass numbers now for the sake of practice I want you to determine the number of protons neutrons and electrons in an atom of nitrogen 15 so this is one of the Isotopes of nitrogen in an ion of aluminum 27 and let's say this ion has a charge of POS 3 and of an ion of let's say sulfur
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34 which has a charge of 2 minus so go ahead and calculate the number of protons neutrons and electrons starting with nitrogen the number of protons will be the atomic number which is the smaller of these two numbers so that's seven the number of neutrons is the difference between 15 and 7 15 - 7 is 8 so we're going to have eight neutrons now because there's no charge here this is an atom and atoms as we said are neutral they have equal number of protons and electrons so this atom has seven
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electrons now in the case of the aluminum cation keep in mind cats have positive charges we need to determine the atomic number first and we could find that in a periodic table so if you look up aluminum you'll see that the atomic number is 13 which means that it has 13 protons now if we subtract 27 by 13 that will give us 14 neutrons now we do have a charge and so the number number of electrons will differ from the number of protons to calculate the number of electrons it's
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going to be the atomic number minus the charge so the atomic number is 13 the charge is posi 3 a negative times a positive is a negative so this becomes 13 - 3 and so that gives us 10 and thus we get 10 electrons and as we said before whenever you have a positively charged ion there's going to be more protons than electrons which we could see that there's three more protons than electrons now let's move on to the other example so let's find the atomic number of sulfur using the periodic table
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sulfur has an atomic number of 16 which means that there are 16 protons now 34 - 16 is 18 so this particular isotope of sulfur has 18 neutrons some other isotopes of sulfur are sulfur 33 and sulfur 32 the one that we're dealing with is sulfur 34 the mass number identifies the isotope number the atomic number identifies the element so anytime the atomic number is 13 you know that the element is aluminum anytime the atomic number is seven the element is nitrogen so the atomic number
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identifies the element and the mass number identifies the isotope within a certain type of element now let's calculate the number of electrons so it's going to be the atomic number 16 minus the charge which is -2 a negative * a negative is a positive so 16 + 2 is 18 notice that we have more electrons than protons because we have a negatively charged ion which is an annion so now you know how to calculate the number of electrons protons and neutrons
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