In this video we're going to learn to name and write the formulas for simple compounds:
ionic compounds, polyatomic ions in ionic compounds and some simple molecular compounds.
For ionic compounds we can start with something relatively simple NaCl. Na as we know from
the periodic table is sodium. We'll capitalize that and then CL is chlorine. In this case
we know that it is chloride so the way this works is the positive ion and from the location
of sodium in a periodic table we know that it has a +1 charge because it's in the first
column group 1A and chlorine likes to have a negative charge. We're gonna change the
suffix of chorine to ide to suggest that it's negative or to indicate that it's negative,
so sodium chloride. Another compound Li2O in this case again notice that we're putting
the element that's going to be a cation first and we know that lithium is group 1A again
so we're going to have a positive charge and oxygen is in ground 6A so if we added 2 electrons,
-2 we would get to the noble gas configuration so we're gonna have a -2 charge on our oxygen.
This is going to give us Llithium oxide and again for the anion we're gonna chnge the
suffix and put ide. Now notice that the name lithium oxide does not indicate the two lithiums
in Li2O but we know that we have to have 2 lithium atoms or cations to match the charge
of the oxygen so therefore we do not need to indicate in ionic compounds how many elements
are going together or ions are going together to make these compounds. These are relatively
simple and notice that I'm changing I'm staying with main group. If we look at a transition
metal so FeF3 we know that this is iron but iron is a transition metal so we don't know
what the charge is right off the bat. We know that fluoride is a -1 and we know that in
this molecule we have three of those so our overall charge is going to be -3. If we're
going to balance our charge in this ionic compound what is the charge that's necessary
for our iron? Well if we have three -1 that's -3 we're gonna need a +3 so therefore this
is going to Fe+3 with three fluoride ions to indicate that in the name we're gonna put
iron (III) and then fluoride so for our transition metals and for those metals that do not have
a definite charge as a cation we're gonna use the roman numeral system behind. Let's
try a couple where we go from the name to the formula. So magnesium oxide we know that
magnesium Mg is in the second column or group 2A so that's can have a +2 charge and oxygen
that we've already looked at has a -2 so therefore we balance that +2 -2 that's zero so we can
just say him MgO as the formula. Let's try another one chromium (III) oxide here we know
gonna be Cr +3 and oxygen -2 now we need to balance this so the correct formula here if
we have +3 and -2 well we're going to have to have two chromiums which brings up this
charge to +6 and we'll need three oxygens, 3 times -2 will give us -6 so we balance our
charge so this would be the correct formula for chromium (III) oxide. These were some
simple ionic compounds. We can make these slightly more complicated by starting to use
polyatomic ions. In polyatomic ions we need to learn the polyatomic ions. I'm gonna list
out a few here but the list is a little longer than this depending on the text you're using.
There's usually only one common cation that's ammonium NH4+. For the anion's there's a really
long list. We have hydroxide OH-, cyanide CN-, nitrite NO2-, nitrate NO3-, notice here
that the ite had one less oxygen than the ate. This is a common system. Carbonate CO3-2,
bicarbonate or often called hydrogen carbonate HCO3-, sulfite SO3-2, sulfate SO4-2, phosphate
PO4-3, perchlorate ClO4-, and acetate this a molecular polyatomic acetate is CH3CO2-.
Now when we get a simple compound with a polyatomic like KNO3 notice that the polyatomic is written
together. We know that the potassium ion combines with the nitrate and so we get potassium nitrate.
Let's look at another example for polyatomics. Notice that we're still using the atomic nomenclature
system here let's take in parentheses NH4 to the 2 and then SO4. We know the NH4 is
ammonium and the SO4-2 is sulfate. You can see here that we had to have two ammoniums
for the one sulfate but in the name it's just ammonium sulfate since we know the charges
of these two polyatomics we should have been able to figure out the name. One more example
calcium going the other way calcium carbonate again calcium is group 2 so that's gonna have
a +2 and carbonate we have to know what that polyatomic is we know it's -2 so therefore
our formula is just CaCO3. This is our simple ionic compounds those with just simple ions,
cations, and anions and those with polyatomics. Now let's look at some molecular compounds.
If we look at two carbon with one oxygen and carbon with two oxygens if we tried to use
the ionic naming system this would just be carbon oxide but we can see here we have two
different forms that's because we're sharing electrons not having a cation and in anion
so when we go to a molecular compound, ones with covalent bonds we need a different name.
What we'll use is for CO that is a carbon with one oxygen so we'll use the prefixes
for one mono we delete one oxygen from mono to get the oxide so monoxide, carbon monoxide
with the CO2 we have carbon again to start but now we have two oxygens so we're going
to use dioxide to indicate two. This is the way that we can indicate the right number.
Notice here that we cannot rely on the cation or the anion to figure out how many of the
two elements put together so we have to be explicit about that and we use the prefixes
to get us the right number. Let's try N2O5, with N2O5 we have two nitrogens so that's
gonna be dinitrogen the oxygen now we have pentoxide so dinitrogen pentoxide so we have
two nitrogens and five oxygens now there are some caveats to this. One of them is those
that contain hydrogen another is those that have specific common names and then we'll
also look quickly at organic compounds. So if we look at hydrogens they often use non-systematic
names so if we look at HCl we're going to call that hydrogen chloride it looks like
a follows the ionic or simple name we just leave out the mono but if we go to something
like H2S this also does not have an indication that we have two hydrogens so here we have
hydrogen sulfide. So you see when hydrogen we live out the prefixes so it's a non-systematic
naming system and this is very common for anything that contains hydrogen. But we also
have some compounds like NH3 that uses a common name nothing that's really related to any
of the elements in there for these there's a set of common names we're going to need
to know. This one you'll see quite often this is ammonia and you may be familiar with that
and another one where we do not use its non-systematic or systematic name dihydrogen oxide or hydrogen
oxide but its common name—water. The other one we need to watch for are organic compounds
specifically hydrocarbons for the hydrocarbons we're gonna learn a list of names or IUPAC
names. This is a group of names that have been decided on and are the official chemical
names for these compounds. For this video I'm just gonna start with a few--one carbon
two carbons and an organic hydrocarbon with three carbons for the first one the IUPAC
approved name is methane, for two carbons ethane, for three carbons propane. It's usually
best to know all of the IUPAC names for hydrocarbons all the way up to 10 carbons but for this
video we just wanted to get you started. Now you should be able to name simple ionic compounds,
ionic compounds that contain polyatomics, and some simple molecular compounds.