How to Speak Chemistrian: Crash Course Chemistry #11


Learning to talk about chemistry can be like learning a foreign language, but Hank is here to help with some straightforward and simple rules to help you learn to speak Chemistrian like a native.


Transcript Provided by YouTube:

00:00
Imagine you wake up one morning, and you’re under a tree, and you don’t recognize anything.
00:05
You’re surrounded by low, grassy hills. It’s raining a bit and smells like waffles and potatoes.
00:11
As you rub the sleep from your eyes, you notice a woman, and she’s like “Qu’est-ce que tu fais dans la pluie?”
00:16
and you’re like “What? Where am I? Was that French? Did I fall asleep in my house and wake up in France?”
00:22
Then another guy walks up, and he’s got a mustache that, frankly, not a lot of other guys could pull off,
00:27
and he’s like “Wa zijde gij hier nu feitelijk aant doen in die regen?” And that was clearly not French.
00:32
And then a little kid comes up with an umbrella, and says “Wat doe je hier buiten in de regen?”
00:37
Okay… Do you know where you are? Give up? Belgium.
00:41
And you know what’s an awful lot like unexpectedly waking up in Belgium with a bunch of people
00:45
speaking several different languages you don’t understand? Chemistry.
00:49
[Theme Music]
00:59
Maybe more than any other scientific discipline, chemistry has its own language.
01:03
Not jargon, though it has that too,
01:05
but a whole system of speaking and writing that’s unique to the study of chemicals,
01:09
a way of translating symbols and numbers of chemical formulas into words that can be spoken.
01:15
Chemistrian, if you want to call it that (and I do), can be tough to learn at first,
01:20
but it can be done, once you know the rules.
01:23
And of course, as with all languages, fluency really only comes with lots of use,
01:27
so I don’t expect you to walk out of this video spouting off about three-keto-two-carboxy-arabinitol,
01:33
but I do want to get you off on the right foot.
01:35
So, talking about chemistry can sometimes be like describing a rainy day in Belgium.
01:39
I mean, all three of those people in the beginning of the video, they were saying the same thing.
01:42
They just used different sets of rules to describe it.
01:46
The woman using French, the kid, Dutch, and the guy with the ‘stache, a Dutch dialect called Flemish.
01:51
So the trick is knowing which rules to apply where,
01:54
and fortunately for Chemistrian, there’s a kind of phrasebook, the Periodic Table.
01:59
Just as there are parts of Belgium where different dialects are spoken,
02:02
the rules for describing an element can change depending on where in the table it is.
02:06
This is especially the case with the things that we’re going to be talking about today: ions and acids.
02:11
These rules apply not only to their formulas, that is, the chemical symbols that we use in equations,
02:16
but also to their names, how we write and say them.
02:20
Let’s start off with ions.
02:22
Atoms become ions by gaining or losing electrons, giving them a positive or negative charge.
02:26
Ions that have lost electrons, and therefore take on a positive charge, are cations.
02:31
Whereas ones that gain electrons to become negative are anions.
02:35
You’ll notice, despite the rules of English, that these are pronounced “cat-ions” and “ann-ions”,
02:40
not “cayshuns” and “aniuns”
02:42
The most basic ions, called monatomic ions, are formed from single atoms.
02:46
To write one as a formula, you just use the chemical symbol of its base element
02:50
and then add the charge as a superscript. That’s it.
02:53
If the charge is just of a single electron lost or gained, you don’t need to write the one,
02:57
but any charge greater than that requires a number.
03:00
So the sodium ion is written like this, while the ion of chlorine looks like this.
03:04
But the names of these ions change somewhat depending on whether they are cations or anions.
03:08
Cations, for some reason, the name is just the element followed by the word “ion”.
03:12
So, in this case, it’s just a “sodium ion”.
03:15
But with anions, you use a special suffix, “ide”.
03:17
So, the anion of chlorine is chloride, and is written so.
03:21
Now, when we name ionic compounds, we just say the cation first, and the anion second.
03:26
You’ve done this.
03:27
You just maybe didn’t know you were doing it. “Sodium chloride”, “hydrogen sulfide”, easy peasy.
03:32
Now in order to figure out what’s what, we have to rely on our handy phrasebook, the Periodic Table.
03:36
The first two columns on the left are your alkali metals, and your alkaline earth metals.
03:41
They all form ions readily when they react with non-metals,
03:44
and when they do, they always lose electrons, forming cations.
03:48
On the other side of the table, you’ll find most of the common anion-forming elements grouped together,
03:52
particularly your halogens, along with oxygen, sulfur, and nitrogen.
03:57
These elements gain electrons to form those negative ions ending with “ide”.
04:02
And you’ve no doubt heard of most of them.
04:03
But here’s a wrinkle. Many elements can form more than one kind of ion.
04:07
Iron, for example, in the middle there, forms cations, but they can have a charge of either two or three.
04:12
This is the case for many of the transition metals in these middle columns of the table.
04:17
They’re grouped together precisely they have these properties in common.
04:21
Everything’s where it is for a reason people, that’s the beauty of it.
04:24
But it’s in this middle region of your language map where really unique dialects start to crop up,
04:28
changing how ions are named and written.
04:31
The formulas for ions here are, thankfully, as easy as anywhere else,
04:34
with the size and polarity of the ion’s charge written as a superscript.
04:38
But when naming these ions, we introduce a whole new naming convention,
04:42
and by new, I mean really, really old. Roman numerals.
04:46
Yeah, Roman numerals still have a practical application beyond telling you which Star Wars movie you’re watching.
04:50
In this case, when saying or writing the name of a transition metal ion,
04:54
you use Roman numerals to denote the size of the ion’s charge, like Iron II or Iron III,
05:00
and you write it this way whether the ion’s in a compound or by itself.
05:05
Just be sure to put the numerals in parentheses with no space between the cation and the first parenthesis,
05:09
because trust me, teachers will mark off for that.
05:11
OK, so I know what you’re probably thinking right now:
05:14
Why, in the name of Pliny the Elder, do we have to use Roman numerals like a bunch of Romans?
05:19
Well, check it out:
05:20
Arabic numerals are already being used to denote how many atoms of an element there are in a molecule,
05:26
the molecule’s charge, its oxidation state, the number of molecules reacting in an equation.
05:30
We didn’t need more Arabic numerals!
05:32
So the chemistrians decided to trundle out the Romans.
05:35
Now, acids are ionic compounds just like any other,
05:37
but when they ionize, their hydrogen ions, just lone protons, become the cation,
05:42
and any negatively charged leftover is the anion.
05:45
So all acids are made up of one or more hydrogen cations bound to an anion.
05:50
Writing the formula of an acid is easy if you know what the anion is.
05:54
Because ClO3 is negative one charge, you can tell that it will bond with just one hydrogen ion to form HClO3. Simple.
06:01
Now, when we name these acids and anions, we have to kind of watch our mouths,
06:05
because in the realm of chemistria, there’s a whole system of prefixes and suffixes that
06:10
you have to keep track of to make sure you’re addressing everyone by the proper title.
06:13
Y’know, you don’t want to offend anyone.
06:14
Once you’ve acquired an ear for it, though,
06:16
you can tell just from the name of an acid or it’s anion what its composition is,
06:21
because these prefixes and suffixes practically give you the formula.
06:24
Specifically, they tell you how many oxygen atoms it has.
06:27
That’s right, even though an acid is defined by its ability to give up hydrogen ions,
06:32
it is identified by it’s oxygen content.
06:34
Eh, when in chemistria.
06:36
Let’s go back to that ClO3 minus. You might know that as the chlorate ion.
06:41
That’s chlorate, with an “-ate”. Not a number 8. A-T-E.
06:45
Like we said, chlorate bonds with a hydrogen ion to form HClO3 which is called chloric acid.
06:51
That’s chloric with an I-C.
06:52
As a rule, all anions that end in “-ate” form acids that end with “-ic”.
06:57
Phosphate ion has a three charge, so it bonds with three hydrogen ions to form phosphoric acid.
07:02
Similarly, the sulfate ion needs just two hydrogen ions to form sulfuric acid. You get the idea.
07:08
These compounds, the “-ic” acids and their “-ate” anions, are really common and familiar,
07:13
so much so that they form kind of a baseline for the language of acids.
07:17
Chlorine, hydrogen, and oxygen can combine to make chloric acid,
07:20
but they can form way more other similar acids.
07:23
And all these variations are named using a special, super-explicit set of prefixes and suffixes
07:29
that tell you whether they have more oxygen atoms or less oxygen atoms than the baseline compounds.
07:35
And by how many. Take HClO2.
07:38
Because we know that the cation is H plus,
07:40
we can immediately see that the anion is ClO2 minus, which we know as the chlorite ion.
07:46
In addition, we can see that HClO2 has one less oxygen atom than HClO3.
07:51
The “-ous” suffix means “less than” and thus gives us our name, chlorous acid for HClO2.
07:57
So the chlorite ion forms chlorous (with an “-ous”) acid.
08:02
And indeed, all atoms that end in “-ite” form acids that end in “-ous”. O-U-S.
08:07
But what if it has two fewer oxygen atoms than it’s “-ic” counterpart?
08:11
For both the acid and its anion, you simply use the suffixes I just mentioned, “-ous” and “-ite”,
08:16
but then additionally, you add a prefix.
08:18
It’s from the Greek for “less than” or “under”: “hypo-“.
08:21
So, HClO is hypochlorous acid, and likewise, it’s anion, ClO minus, is hypochlorite.
08:29
But there are still a couple of scenarios that we haven’t considered yet.
08:32
Like, what if an acid has one more oxygen than the “-ic” version?
08:35
In that case, you use a different prefix, using “per-“, Latin for “very” or “thoroughly”.
08:41
Sounds like it’d be fun to find some uses for that “per-“. Let’s do it.
08:44
There’s perplexed, like very plexed. Pervaded, thoroughly invaded. Perfect, very… fect.
08:51
I had to look it up. It’s from the Latin for “to complete”.
08:55
So “perfect” is to complete something thoroughly. I like it.
08:58
So the “per-” prefix is just a way of saying “thoroughly oxygenated”, completely, in fact.
09:03
If you see the “per-” prefix, that’s the highest number of oxygens that can get on there.
09:08
So HClO4 is perchloric acid and it dissociates into an anion called perchlorate.
09:14
And what if, brace yourself, the acid doesn’t contain any oxygen at all?
09:18
Remember, hydrogen is the key player in acids, so even though oxygen is common, it’s by no means required.
09:22
When a hydrogen bonds with chlorine to form an acid, since there’s no oxygen it’s just called hydrochloric acid,
09:29
and it’s anion follows the same rules for anions we talked about at the very beginning,
09:32
ending in “-ide”, in this case, chloride.
09:35
Now, considering what just happened to you here,
09:37
there’s a 99% chance that you’re now more confused than you would be if you woke up in a drizzly Belgian meadow.
09:42
So, if that’s the case, get a pencil and get ready to pause the video.
09:45
Now, copy this table down. It’s all you need to know.
09:49
Be familiar with the “-ate” ions and the “-ic” acids
09:51
and then simply cobble on the appropriate prefixes and suffixes based on the number of oxygen atoms present.
09:57
It might not be as fanciful as waking up in a Belgian meadow, but it is enlightening.
10:01
Just look at all the stuff we learned, like how to determine the formulas and names of mono-atomic ions,
10:07
how to find cation and anion forming elements on the Periodic Table,
10:10
how to write the formulas and name transition metals, and how to name acids and their anions.
10:16
Thank you for watching this episode of Crash Course Chemistry, which was written by Blake de Pastino.
10:20
The script was edited by me, and our chemistry consultant was Edi Gonzalez.
10:24
This episode was filmed and edited and directed by Nicholas Jenkins.
10:27
Our script supervisor and sound designer was Michael Aranda and our graphics team is Thought Café.


This post was previously published on YouTube.

Photo credit: Screenshot from video