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Lecture Comments (87)

3 answers

Last reply by: Professor Hovasapian
Wed Aug 15, 2018 6:42 AM

Post by Nick Jiang on August 14 at 10:28:00 PM

Hi Professor,
I have a few questions:
1. Is every compound that has hydrogen an acid? If so, why?
2. Kind of relating to my last question, I don't understand why we can't name H2SO4 as hydrogen sulfate. But there's also HSO4- for hydrogen sulfate.


1 answer

Last reply by: Professor Hovasapian
Tue Jun 19, 2018 5:55 AM

Post by Neeraj Lalwani on June 17 at 09:12:17 PM

Hello Mr. Hovasapian,
Just a quick question: Why did you choose to write acetate as (AcO)- rather than (C2H3O2)-?

1 answer

Last reply by: Professor Hovasapian
Mon Jan 8, 2018 4:22 AM

Post by Amy Zhang on January 6 at 10:55:46 AM

In the Sixth Editio Zumdahl Chemistry textbook you recommended to me, it says that the periodic table groups can be written as either 1-18, or with letters like 3A, 4A, etc. However, besides in the textbook, I've only ever seen the 1-18 and not the letter names. Is that like a new thing now, as the textbook was printed in 2003?

1 answer

Last reply by: Professor Hovasapian
Wed Jan 3, 2018 3:54 AM

Post by Qiaoxiang Dong on December 26, 2017

Hi Prof Hovasapian!

How would you name a covalent compound with a subscript that is greater than 10? Would you use other prefixes?

Calvin Huang

1 answer

Last reply by: Professor Hovasapian
Thu Aug 31, 2017 5:40 AM

Post by Yosef Charkatli on August 30, 2017

Greetings professor Hovasapian!
I just wanted to thank you for your great lessons and let you know that I was able to score a 4 on the AP chemistry test by relying solely on your lessons, and I am sure that if I payed a little more attention to your lessons I would have scored a 5.  You made this course a lot easier for me and you truely are the best chemistry teacher I have learned from. I simply can't thank you enough.
Best regards.

1 answer

Last reply by: Professor Hovasapian
Fri Aug 18, 2017 3:12 AM

Post by Carlins Almonor on August 16, 2017

My teacher includes the naming of hydrates in our assessments. How would one go about naming hydrates?

3 answers

Last reply by: Professor Hovasapian
Fri Jul 21, 2017 8:15 PM

Post by Amy Zhang on July 20, 2017

Hi Professor! I was wondering if you could give me the names and links for instructional textbooks and practice workbooks that follow your AP Chemistry course. Thanks!

2 answers

Last reply by: Kenneth Dietz
Mon Jul 17, 2017 1:22 PM

Post by Kenneth Dietz on July 10, 2017

so whats the story with compounds like monosodium glutamate?  Is it just not following the rules.  Not following these rules seems common on labels of ingredients. ( trisodium phosphate?) Is it just a different system?

1 answer

Last reply by: Professor Hovasapian
Tue Oct 25, 2016 10:56 PM

Post by Anu Yelisetti on October 25, 2016

Hi Prof. Hovasapian!
I just wanted to let you know that so far your lectures have helped me so much in school and I really enjoy them!
I don't have any specific questions pertaining to this video, but I had one about the overall course. I take Honors Chemistry in school right now, which does cover some of the basic concepts covered in AP chemistry, and I wanted to take the AP test for Chemistry this year, so would completing the course on this website be enough preparation, or would I have to take another "self-study" class outside of school? Currently, I've been using this site and reading the Chemistry textbook by Zumdahl. I'd really appreciate your feedback!
Anu Yelisetti

2 answers

Last reply by: Professor Hovasapian
Mon Jun 27, 2016 7:07 PM

Post by Mohamed E Sowaileh on June 19, 2016

Hello Dr. Hovasapian,

Is 2 months period enough to finish the whole course, or you don't recommend that? and is it sufficient to study from your lectures only without textbooks to gain full understanding?

1 answer

Last reply by: Professor Hovasapian
Wed May 11, 2016 2:33 AM

Post by Mohamed E Sowaileh on May 9, 2016

is this course suitable for a collage level? I mean the details.  

1 answer

Last reply by: Professor Hovasapian
Sat Oct 24, 2015 7:02 PM

Post by Karthik Gnanakumar on October 24, 2015

Hello Prof. Hovasapian!

This a question not pertaining lesson specifically, but the whole AP Chemistry course you are teaching as a whole. All I wanted to ask is that if the AP Chemistry Lectures you teach are up-to-date. CollegeBoard is changing things up and the AP courses have new set of foundations being built upon. So do these lectures you teach pertain to the newer version of the AP Test or the old AP Test?

Thank You,
Karthik Gnanakumar

P.S: I love your lectures! Keep up the good work. The way you teach really helps me understand the subject.

1 answer

Last reply by: Professor Hovasapian
Mon Oct 19, 2015 12:04 AM

Post by Xinyuan Xing on October 17, 2015

Hi Professor Hovasapian,

I'm Alina from China. Just want to go back here to say Thank You. I've got a 5 on my AP chemistry, and your lectures are basically all my preparation materials. Thank you so much for your dedicated  lectures! They are great lectures for students (including me) who desperately want to learn under a situation that no one around them is familiar with the subject.

Wish you all the best,

1 answer

Last reply by: Jim Tang
Sat Jul 18, 2015 9:59 PM

Post by Jim Tang on July 18, 2015

Wait, isn't acetate C2H3O2-? Where did you get AcO?

2 answers

Last reply by: Professor Hovasapian
Fri Jul 10, 2015 4:12 PM

Post by Jinbin Chen on July 7, 2015

Hi, Mr. Raffi.

I am writing this comment to thank you for this AP Chemistry lecture series. I was going  to merely learn some basic chemical principles when I started this series last summer, but I ended up changing my mind about my future majors because of these lectures. I checked my AP scores for chemistry today, and I got a 5 on it. Now I am planning to get a degree in chemistry (or some related field such as engineering), and I thank you for your effort to teach chemistry as clearly as possible so that people can appreciate this subject.

I do have a few questions though. Is the analytical chemistry lab a good substitute for general chemistry lab? I self-studied the entire AP curriculum, so I do want some exposure to the lab techniques without having to do general chem lecture again (since they tied the lecture and lab together). Also, are topics such as transitional metals and nuclear chemistry important later on for chem majors (these topics are left out completely in AP)?


1 answer

Last reply by: Professor Hovasapian
Sat Jun 20, 2015 4:51 PM

Post by Katie Early on June 19, 2015

Professor Hovasapian- I just wanted to let you know that I took Biochemistry last year and it was your lessons that got me through it. I currently teach high school Chemistry, but I do not enjoy biochem and organic as much as straight inorganic. I am preparing to teach AP Chemistry and these lessons help better than anything I can find for those little "reminders." You are so awesome!
Thank You,
Katie Early

1 answer

Last reply by: Professor Hovasapian
Thu Mar 12, 2015 3:30 AM

Post by Richard Meador on March 5, 2015

The periodic table shows that the number of protons per element increases from 1 (Hydrogen) to 111 (Rg).  Why are there no gaps? In other words, what in the formation process caused there to be no gaps in the rising number of protons per atom?  

1 answer

Last reply by: Professor Hovasapian
Mon Mar 2, 2015 11:16 PM

Post by aimun amatul-hayee on March 2, 2015

do the transition metals have a charge

1 answer

Last reply by: Professor Hovasapian
Mon Mar 2, 2015 11:12 PM

Post by aimun amatul-hayee on March 2, 2015

how does calcium phosphides charge equal 0 if the formula is Ca3P2

2 answers

Last reply by: Andrew Lewis
Wed Mar 11, 2015 10:01 PM

Post by Hayley Gao on December 23, 2014

I can't watch any videos on this web. it's just show network error, but i can use any other webs and i still have the membership. Could you help me about that? Thanks!

1 answer

Last reply by: Professor Hovasapian
Thu Nov 6, 2014 1:34 AM

Post by Shih-Kuan Chen on November 5, 2014

Dear Dr. Hovasapian,

Do you think you could provide a list of signs and names of polyatomic anions that will possibly appear on the AP exam?

1 answer

Last reply by: Professor Hovasapian
Fri Aug 22, 2014 8:43 PM

Post by Okwudili Ezeh on August 22, 2014

Please could you tell me the difference between your own course and the other 2 general chemistry courses that are being offered on this website?
Are you covering more material?

1 answer

Last reply by: Professor Hovasapian
Tue Jul 1, 2014 6:56 PM

Post by Jerry Liu on June 30, 2014

Is this course still relevant to the new and updated AP test?

2 answers

Last reply by: Datevig Daghlian
Fri Jun 27, 2014 11:33 AM

Post by Datevig Daghlian on June 12, 2014

Dear Dr. Hovasapian,

    Thank you for responding to my previous question--your guidance and passion for chemistry is greatly seen in your lectures and your effort in teaching chemistry. I would ask you one more thing--I am currently home schooled and am in my Junior year. I have been looking around for an online, interactive AP Chemistry course and wanted to ask you if you had any particular recommendations? Please if you can let me know, I will be very thankful! Thanks again for your giving of your valuable time to assist me!

Thank You,
George Daghlian

2 answers

Last reply by: Datevig Daghlian
Wed Jun 11, 2014 9:47 AM

Post by Datevig Daghlian on June 10, 2014

Dear Dr. Hovasapian,

    I would like to thank you for your passion in teaching and explaining the concepts of Chemistry. This coming year I will be taking AP Chemistry. Not having any chemistry background, how do you recommend I should prepare over the summer? Any insight you can give is greatly appreciated! God Bless!

Thank You,
George Daghlian

1 answer

Last reply by: Professor Hovasapian
Sun Jun 8, 2014 3:43 AM

Post by Jinbin Chen on June 6, 2014

Hi, professor!

I am very interested in starting this chemistry course, but the last time I took a chemistry class was two years ago (and it was very basic). Should I watch some other chemistry videos in this site before starting AP Chemistry?

By the way, the new AP Chem test is being administered starting from this year. Are you planning to post some new videos regarding the change in this exam?

Thanks and take care!

1 answer

Last reply by: Nada A.
Tue Nov 5, 2013 5:51 AM

Post by Nada A. on November 5, 2013

PCl5 ---> PhosphourPetaCloride ? it is ending with ide... doesnt that mean its an Ion? and its not... shouldn't it be PhosphoursPetaChlorine?

3 answers

Last reply by: Professor Hovasapian
Fri Nov 1, 2013 12:30 AM

Post by robina saeed on October 31, 2013

Hi Professor,

Is this a good course to prepare for the MCAT chemistry section or would I need to stick with a textbook?  thanks and take care

0 answers

Post by yannick Haberkorn on October 9, 2013

at 17:08 i thought nitrogen carried a -3 charge and not a - 1 charge .. could someone please clarify

1 answer

Last reply by: Professor Hovasapian
Wed Oct 9, 2013 4:52 PM

Post by yannick Haberkorn on October 9, 2013

at 17:08 i thought nitrogen caries a -3 charge and not a -1 charge ? its not really clear

1 answer

Last reply by: robina saeed
Fri Aug 2, 2013 2:10 PM

Post by robina saeed on August 2, 2013

Hi Professor
Thanks for the earlier response. I have one more question. I have had a full year of general chemistry.  Do I need organic chemistry to begin this course?


1 answer

Last reply by: Professor Hovasapian
Thu Feb 28, 2013 4:39 PM

Post by Youssef Sadki on February 28, 2013

I wpould like to thank you so much ...you make really like how easy to drink water...

0 answers

Post by Professor Hovasapian on February 18, 2013

Hi Raj,

I hope you're doing well. Thank you for your kind words, and I'm happy to hear you are enjoying AP Chem.

Regarding the OH, I'm wondering if you meant the OH- polyatomic Ion. If so, then, because it is an Ion that has a charge of -1, it is named as a single entity, and does not fall under the systematic procedures for naming compounds -- we simply rfer to it s Hydroxide.

Hydrogen Peroxide is actually H2O2. Now, O2- (an Oxygen atom with a 2- charge) binds to to H+ ions to create this molecule.

If the molecule were HO, without a charge, then you would be correct: it would be called Hydrogen Monoxide. In fact, water, which is the common name, and which you know as H2O -- it's systematic name is exactly Dihydrogen Monoxide.

If I have misinterpreted you question, Raj, please let me know, and I will remedy the issue.

Best wishes for a happy and productive year.


0 answers

Post by rajendra irani on February 18, 2013

HO -Hydrogen peroxide. why not it is named as hydrogen monoxide?

0 answers

Post by rajendra irani on February 18, 2013

Dear Sir,
Great Teaching and I am really enjoying AP Chemistry.

Kind Regards

1 answer

Last reply by: Professor Hovasapian
Tue Jan 29, 2013 3:37 PM

Post by Antoni Szeglowski on January 27, 2013

Best teacher on Educator!

0 answers

Post by Riley Argue on June 14, 2012

I sat in first year chem in high school for a complete year, but my teacher could not explain this material to save her life.

But somehow you explained it so simply. Thank you!

0 answers

Post by Yaron Zaret on June 10, 2012

awesome teacher

0 answers

Post by Abdihakim Mohamed on May 7, 2012

Where where you professor for the past two years of my life, I wish I came across this website way earlier.

0 answers

Post by mateusz marciniak on May 5, 2012

great video but i was wondering, isn't Acetate C2H3O2 -1?

0 answers

Post by Miguel Suarez on April 6, 2012

Nice video really good work professor, wish all professor would explain like you

Naming Compounds

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Periodic Table of Elements 0:15
  • Naming Compounds 3:13
    • Definition and Examples of Ions
    • Ionic (Symbol to Name): NaCl
    • Ionic (Name to Symbol): Calcium Oxide
    • Ionic - Polyatoms Anions: Examples
    • Ionic - Polyatoms Anions (Symbol to Name): KClO
    • Ionic - Polyatoms Anions (Name to Symbol): Potassium Phosphate
    • Ionic Compounds Involving Transition Metals (Symbol to Name): Co₂(CO₃)₃
    • Ionic Compounds Involving Transition Metals (Name to Symbol): Palladium 2 Acetate
    • Naming Covalent Compounds (Symbol to Name): CO
    • Naming Covalent Compounds (Name to Symbol): Nitrogen Trifluoride
    • Naming Covalent Compounds (Name to Symbol): Dichlorine Monoxide
    • Naming Acids Introduction
    • Naming Acids (Name to Symbol): Chlorous Acid
    • % Composition by Mass Example

Transcription: Naming Compounds

Hello, and welcome to Educator.com; and welcome to the first lesson of AP Chemistry.0000

Today, I'm going to start by discussing the naming of compounds, because we have to know what it is that we are dealing with in order for us to jump into the chemistry.0005

So, let's get started.0013

OK, so this is, of course, the periodic table, and I'm just going to do a quick overview of the periodic table, just to get a sense of where we need to be, because this periodic table is what you are going to be using all the time--it's going to be your primary reference in chemistry--as you already know.0017

Over here, on the left, we have this first column; these are called the alkali metals.0033

Actually, you know what?--let's sort of break it up broadly.0040

Generally, everything from about right here onward--everything that is blue, and this orange right here--so the whole left side--these are all metals.0044

Up here, starting with boron, silicon, arsenic, tellurium--everything here and up to the right--those are going to be nonmetals.0053

So, as you can see, most of the periodic table--most elements (naturally occurring elements) consist of metals.0060

These over here are called the alkali metals; the second column is called alkaline earth metals; these here, in the middle--these are called the transition metals.0066

These over here are called the noble gases, basically because they are unreactive.0078

These are called the halogens.0084

These are the standard nonmetals.0086

The only thing on the left that is a nonmetal is hydrogen.0088

Now, let's talk about some of the diatomic gases.0091

There are certain gases (well, certain compounds; not just gases, because bromine is actually a liquid)--certain compounds that occur...0096

The periodic table lists actual atoms; astatine, iodine, bromine, chlorine, fluorine, oxygen, nitrogen, and hydrogen--they occur as diatomic gases.0105

In other words, there are two atoms that make a molecule of that in the natural, normal state.0116

What you are breathing right now is nitrogen and oxygen gas; not nitrogen and oxygen atoms, but there are two atoms stuck together to form a molecule.0121

That is really all that you have to know.0132

These numbers up on top (the ones right below the symbols): those are the atomic numbers--that is the number of protons and electrons in a neutral atom.0135

This number, right down below it (which, for many things, is almost double the atomic number)--that is the atomic mass; that is an average of all of the masses of the isotopes, depending on the frequency of occurrence of the particular isotope.0144

Again, if any of this is strange--things or words like isotope and stuff--I would definitely urge you to look through it in your books, but for all practical purposes, it won't come up all too often.0162

So, I just wanted you to get a quick overview; and now, we can jump into actually naming the compounds.0174

Because, before we do anything else--many of the problems are not going to actually have equations for us, or symbols for us; they're just going to give us names of compounds.0179

We have to know what it is that we are writing, so we can write an equation--all chemistry begins with a chemical equation.0187

OK; let's start off, quickly, by talking about what ions are.0193

Ions are atoms that have lost or gained an electron--that is it; lost or gained one or more electrons.0201

Your atoms (your naturally-occurring atoms) are neutral; in other words, they have the same number of protons and electrons, which makes them electrically neutral.0223

If I add to those, or if I take away from those, all of a sudden they become charged particles.0231

Positive ions are called cations, and negative ions are called anions.0237

So, an example of that would be something like this: Mg2+ is a magnesium atom that has lost two electrons.0252

Because an electron is the thing that is being added or subtracted, when we add (electrons are negatively charged), it carries a negative charge.0259

So, for example, O2-; that is an atom that has gained two electrons, so now it's carrying two extra negative charges.0268

Magnesium lost two electrons, so now it has two more positive charges than it does negative charges; that is why we put the 2+.0277

Fluorine is -; potassium is +; aluminum is +3; iron(II) is that; there is also an iron(III)--and we'll talk about that in a minute--why it is that certain transition metals actually can lose more than one electron, and they have different oxidation states.0285

That is it--ions, and the first thing that we're going to discuss, of course, is ionic compounds: simple binary ionic compounds, where the cation is made of one element and the anion is made of the other element.0306

Let's go ahead and get started.0319

OK, so now let's go to ionic, and we're going to go from the symbol to the name.0323

We need to be able to go from the symbol and be able to name the compound, and we need to be able to go backwards (from the name to the symbol).0331

So, from symbol to name--we'll do that first.0338

NaCl...now, if you look at your periodic table, you're going to notice that the alkali metals on the left, the alkaline earth metals (which is the second), and then on the right (if you ignore the noble gases), you're going to have the halogens, and then you're going to have the next group and the next group, working to the right.0344

As it turns out, the metals always lose electrons; nonmetals always gain electrons.0365

So, when we're talking about ionic compounds, it's always going to be the metal that is going to be positive, and it's going to be the nonmetal that is going to be negative.0376

Now, what we do when we put together ionic compounds is: we are just putting them together in such a way that we actually cancel the charge.0385

But again, we will get to that in just a minute, when we're dealing with name-to-symbol.0394

So, sodium...this NaCl, the name for this is sodium chloride--that's it.0399

Anytime you see something like this, basically, what you do is you take the name of the metal (sodium); you take the base of the nonmetal, and you add -ide to it; that's it.0404

How about MgBr2; OK, this is just magnesium, and this is bromine, so it becomes "bromide."0422

That's it; it is always consistent--it's the name of the cation first (the positive, or the name of the metal, first), and then the name--the root of the nonmetal, plus -ide.0436

All binary ionic compounds are named like this.0446

How about something like this: Al2O3; don't worry about what the numbers mean yet--we'll get to that in just a minute.0451

This is aluminum oxide.0460

And then one more for good measure: K2S; this is potassium sulfide.0465

That's it; very, very nice.0477

OK, so now we're going to do to ionic, and we're going to go from the name to the symbol.0479

OK, so if I see something like calcium oxide, how do I symbolize that?0489

Well, here is where we have to actually look at the charges; and the charges come from their arrangement on the periodic table.0499

The alkali metals are in the first group on the left; when they react with nonmetals, they actually lose one electron; they're in the first group.0506

The things in the second column (like magnesium and calcium)--they lose two electrons when they react.0517

Well, if we go to the right-hand side of the periodic table (ignore the noble gases), the halogens--they actually gain one electron when they react.0525

The next column over (next to the halogens), the one where oxygen and sulfur are--they gain two electrons.0538

Then, if you go one more, you're going to end up with the nitrogen and phosphorus column; those gain three electrons.0544

So, when you're putting ionic compounds together that consist of a metal from the left and a nonmetal on the right, you look at their charges.0553

In the case of calcium, calcium is a 2+ charge, because it's in the second column.0560

Oxygen has a 2- charge, because it is the second column over, ignoring the noble gases; it has a 2- charge.0566

What we're trying to do here is: we need to combine these in such a way that the charges actually cancel.0574

Here, the positive 2 and the minus 2 cancel, so the symbol is just CaO.0580

In other words, I just need one calcium atom and one oxygen atom to make calcium oxide; the charges balance.0585

OK, now let's do something like sodium sulfide.0594

Sodium sulfide: well, sodium is in the first column, so it has a +1 charge; sulfur has a -2 charge; it's in the second column over from the halogens (again, ignoring the noble gases).0603

Well, this is a +1 and this is a -2; in order to balance this charge, this +1 needs to be +2 to balance this -2.0615

Therefore, we need 2 sodiums; so, the symbol becomes Na2S.0623

I need two sodiums for a total 2+ charge to balance the -2 charge.0628

And again, all ionic compounds have to be neutrally charged--their charges have to balance.0632

Let's do something like aluminum iodide.0641

Aluminum is in the 1, 2, third column over on the periodic table, when you actually skip the transition metals (we're going to get to the transition metals next--they are handled a little differently).0652

So, from your perspective, the first column, the second column...you skip the transition metals, and you go to the other column, where aluminum is.0661

That is a 3+ charge, so everything in that column carries a 3+ charge.0670

Al3+; and iodine is a halogen, so it has a -1; well, how many iodines do I need to balance the 3+ charge? I need three of them.0675

So, this becomes AlI3, aluminum iodide.0684

Let's try calcium phosphide.0690

Calcium phosphide is Ca2+, because calcium is in the second column; phosphorus is in the third column over, so it carries a negative 3 charge when it's reacting with a metal.0701

Well, how do I balance 2+ and 3-? I can't do it directly, so I need the least common multiple of these.0711

The least common multiple is 6.0717

In order to make 6 positive charges, I need 3 calciums; and 6 negative charges--I need 2 phosphoruses.0720

So, this becomes calcium phosphide; that is it.0729

You're just taking a look at the charge on the anion and the cation, and you're arranging them--taking specific numbers of them and putting them together so that the charge is 0--that's all you're doing.0732

We'll finish it off with aluminum sulfide.0743

Aluminum sulfide: OK, we said that aluminum was 3+, and sulfur is in the column with oxygen, so it is a 2-; so again, we have to make 6, so we end up with Al2S3, aluminum sulfide; that is it.0750

OK, now we'll do polyatomic anions.0765

Polyatomic anions: again, you have seen them before; polyatomic anions are anions that are made of more than one atom.0776

Some examples would be something like ClO3-; that is chlorate; SO42-; that is sulfate; maybe PO43-; that is phosphate.0788

Let's see...ClO2-; that is chlorite; and one of the things you are going to notice with the polyatomics--they generally tend to end in -ate or -ite--most of the time.0808

There are some exceptions, like, for example, the NH4+; that is called ammonium.0820

Now, of course, you have seen lists of polyatomic ions; and there is a page, a list, in your book, of polyatomic ions; or, you can go on the Internet, and you can find a list of polyatomic ions--some short, some long--and it lists all of the polyatomic ions that are available.0828

These are treated exactly the same way as the regular atomic anions, in the sense that you are treating them as a whole.0846

When you name them, you just basically use the entire name of the anion; so these actually work out really, really easily.0855

So, let's go from symbol to name first.0863

Symbol to name: for example, if I saw something like NaClO3; well, Na is sodium, and ClO3...when I look it up on the polyatomic ion chart, it is chlorate; so the name is sodium chlorate--very, very simple.0870

If I have something like KClO, well, K is potassium, and if I look up ClO, it is going to be hypochlorite.0891

So, it is potassium hypochlorite.0902

If I had Ca(CN)2, well, Ca is calcium, and CN--when I look it up, it is cyanide; so it is calcium cyanide.0908

So it's very, very simple--you are handling it the exact same way: the name of the metal first, and then the name of the polyatomic anion.0923

Again, these are treated as a whole; it's like--just think of it as one unit that happens to have a specific charge on it: it could be -1, -2, -3...that's it.0929

And again, there is a whole list of these atomic...you will use them enough times so that you'll eventually memorize them, or perhaps you already have them memorized.0940

OK, so now let's go the other way; let's go from the name to the symbol.0949

Now, let's go from name to symbol.0955

Let's do potassium phosphate.0960

If you see "potassium phosphate," well, potassium is in the first column; so, when it reacts as an ion, it is K+.0963

When you look up "phosphate," it is PO43-; we are doing the same thing.0977

We just need to put them together in such a way that the charges balance.0982

In order for the charges to balance, we need three potassiums in order to balance the three negative charges; so we write it as K3PO4: potassium phosphate.0986

How about something like aluminum nitrate?0999

Well, aluminum has a 3+ charge; nitrate, when you look it up--it is NO3, and it carries a -1 charge.1008

I need three nitrates to balance the 3+ on the aluminum, so it becomes Al, and whenever you need more than one polyatomic, you of course put it in parentheses, so it is written as (NO3)3.1016

Now, this three--that means you have three NO3s; so it's three nitrogens, nine oxygens.1030

Now, let's do one more: magnesium hydroxide.1037

OK, magnesium is a 2+; hydroxide, when you look it up--it is a -1; you need two of these to balance the 2+ charge.1047

So, it is Mg(OH)2; good--nice and easy.1054

OK, so now we're going to move on to ionic compounds involving transition metals.1060

Ionic compounds involving transition metals: OK, now let's take a look at two compounds, just to start with.1069

Let's take a look at Fe2O3, and let's take a look at FeO.1084

Well, if I ask you to just name these the way we have been doing, you take the name of the metal; you take the name of the anion, add -ide to it, and you will get iron oxide.1091

Well, it's true--this is iron oxide; however, there is this other compound, that is FeO; this is also iron oxide.1101

These are two entirely different compounds with completely different chemistry; how do we differentiate between the two?1109

As it turns out, transition metals (all of those things in the middle of the periodic table)--they can actually lose different numbers of electrons--the same atom.1114

For example, you can have iron 2+, iron 3+; you can have manganese 2+, manganese 4+, manganese 6+...so these things--we actually have to specify, in parentheses, in the name, how many electrons it has lost--in other words, its charge.1124

So, in this case (and here is how you actually end up doing it), let's take Fe2O3.1140

Fe2O3; well, what do we know about oxygen? Oxygen, when it reacts, always carries a -2 charge.1149

There are three oxygens, so the total charge is -6.1156

Well, this -6 has to be balanced by a +6, because this is a neutral compound, right?--it's neutral.1160

This +6 charge is divided among two irons; that means that each iron is carrying a +3 charge; so what we do is: we write III in Roman numerals, in parentheses, right after the iron.1167

So, it's not just iron oxide; it's iron (III) oxide.1183

This thing in parentheses tells me the charge on an individual iron atom.1186

Now, if you want, you can write it as...it depends on your teacher; I actually use Arabic numerals instead of Roman numerals, so I just write iron (3), like this: iron (3) oxide; it really doesn't matter.1191

Some teachers like Roman numerals--it's more traditional; some teachers actually don't really care; but obviously, depending on your teacher...if they want Roman numerals, give them Roman numerals.1204

You don't want to be losing a point here and a point there for silly reasons like that.1215

Now, this one--how about iron oxide: which iron is this one?1220

Well, oxygen is -2; there is only one of them, so it's -2; that means it has to be balanced by a +2.1224

This +2...there is only one iron here, so this is actually iron (2) oxide.1231

So, when we are naming transition metal compounds, we have to specify the charge on the transition metal.1236

The charge is different, depending on how it has reacted: we express that with these parentheses.1243

Let's do a few of them.1249

Let's do Co2(CO3)3.1252

Now, again, these transition metals--they can react with individual atoms, nonmetals, or they can react with polyatomic ions.1267

Here, we have a cobalt that has reacted with a carbonate.1275

Carbonate--when you look it up, you know the name--it's carbonate; the charge on carbonate is 2-.1279

The charge on carbonate is (you know what, I'm going to do this a little lower, so I can...let me put it over here...Co2(CO3)3) -2.1287

There are three of them, so it gives us a total of -6.1300

This -6 has to be balanced by a +6, because cobalt carbonate is neutral; and this +6 is actually divided by...there are two cobalts that are carrying that total of 6 charge, so each cobalt has a +3.1303

So, we name this cobalt (3) carbonate.1321

That is it--very, very straightforward.1327

Let's do one more: let's do Mn(SO4)2.1330

When I look up SO4)2, or if I know it, I know that SO4 is sulfate; it has a -2 charge; there are two sulfates, therefore the total charge is -4.1336

That is going to be balanced by a +4, because this is neutral.1345

There is only one manganese, so that one manganese is carrying the entire 4 charge.1348

So, this becomes manganese (4) sulfate.1352

That's it--very, very straightforward.1361

OK, so now, let's go from name to symbol.1364

Name to symbol: let's say we have something like palladium (2) acetate.1371

OK, these are really, really simple; they are handled exactly the same way: you are given the charge on palladium--it's right there in parentheses; it tells you that it's a positive 2.1382

Acetate, when you look it up--it is going to be (I'm going to symbolize it as AcO) a negative 1 charge, so palladium acetate...well, this is -1; this is +2; which means you need 2 of these to balance that +2 charge.1390

So, you end up with Pd(AcO)2; that's it.1403

Let's try chromium chloride.1415

Let's give ourselves a little bit more room here; I don't want to use up too much here.1419

Chromium (6) chloride: OK, chromium (6)--that is Cr+6 (or 6+; it doesn't matter--I actually generally tend to write it with the number first).1425

And then, chloride is a -1 charge; well, we need 6 of these to balance that.1440

So, what we get is CrCl6.1445

That's it; that is chromium (6) chloride.1449

If it were chromium (4) chloride, it would be CrCl4; chromium (2) chloride--CrCl2; nice and easy.1451

So now, we have done ionic compounds; now we're going to name covalent compounds.1466

Naming covalent compounds: a covalent compound is a compound that consists of a nonmetal-nonmetal bond.1473

Ionic compound--it always involves a metal with a nonmetal; covalent is nonmetal-nonmetal.1488

Nonmetal-nonmetal bond: OK, so now let's go from symbol to name.1499

If we have something like PCl5; all right, so phosphorus and chlorine--they are both nonmetals.1510

When we name these, the -ide ending stays the same, but what we use is: we need to specify the actual numbers here now--how many (oops, let me get rid of these lines--so PCl5) of each atom there is; and we use the prefixes mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octo- or octa-, nona-, and deca-; so, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.1518

This would actually be called phosphorus (actually, I think that is spelled with a u; you know what, I can't even remember now) pentachloride.1563

Now, notice: when this first atom only has one atom in it, we don't use the mono- prefix; we just say phosphorus pentachloride, carbon dioxide.1582

However, if we had something like this: CO; if the subsequent atoms after the first have just one atom--this is carbon monoxide.1595

We use the mono- for subsequent atoms; we don't use it for the first atom.1608

That is carbon monoxide; and let's see--let's try N2O; N2O is dinitrogen monoxide.1614

You might have something like N2O5, which is dinitrogen pentoxide (you could say pentaoxide, but...it's up to you; I say pentaoxide; you could just drop the a, and do pentoxide).1629

Again, very, very simple--just specify the number of atoms that you have; that is all you are doing.1649

OK, so now, let's go from name to symbol.1654

Name to symbol: let's do nitrogen trifluoride--very, very simple.1662

Nitrogen trifluoride--just put them in: NF3; probably the easiest thing in the world.1671

Let's see; let's try dichlorine monoxide; that is going to be dichlorine, Cl2, monoxide, O: Cl2O; that's it.1677

OK, now let's go ahead and finish up with a discussion of how to name acids.1693

Naming acids: Acid...basically, you are going to have some anion, any anion, balanced by an appropriate number of hydrogen ions.1702

Now, acids are interesting; hydrogen is in the first column; it's right above the alkali metals.1734

When it loses an electron, it loses one electron completely, so it becomes H+; well, H+ reacting with some anion (which is maybe a 1-, 2-, 3-)--they're going to combine.1739

Acids are a little different, because...some people consider them ionic compounds; some people consider them covalent compounds; acidic behavior is more about behavior.1758

We will, of course, talk about acids in detail a little bit later on (in fact, in a couple of lessons), and then again in the middle of the course.1768

But right now, we just want to worry about naming them.1775

An acid is always going to have the H first; so if you see something like this: CH4; that is not an acid.1778

But, if you see something like HCl, that is an acid.1785

Just by convention, again, the cation (which, in this case, is the hydrogen) comes first.1789

Let's go from symbol to name.1794

Let's say that we have something like HBr.1798

All right, now this is called hydrobromic acid.1802

OK, here are the rules.1812

When an acid does not have...well, actually, I'm going to do this a little bit differently.1817

Let me write one more, H2S, so that you can see the pattern: hydrosulfuric acid.1836

When we are dealing with a binary acid...binary means that it's a certain number of H's, and the anion is actually just a single atom--bromide, fluoride, sulfide, iodide, things like that); when it's just those two, it's a binary acid.1849

Now, if it doesn't have oxygen in it--there is no oxygen--then the prefix is hydro-, and then it ends with an -ic; so, hydrobromic, hydrosulfuric...if you saw HCl, this is going to be hydrochloric.1869

Again, notice, we take the root...the root...the root, and we add -ic to it, and that is always consistent.1905

If you have a binary acid that doesn't have any oxygen in it, that doesn't have any polyatomic ions, it is always named the same way.1913

So, let's say HI; this is going to be hydroiodic.1923

It's always a hydro- prefix and an -ic ending, always; there is no exception.1932

Now, let's do something else; let's say if you see an acid like this: H2SO4, or if you see HClO3, or if you see H2SO3, or let's say HCm...no, that's going to be a couple of different things...let's say HNO3.1942

OK, these acids actually have oxygen in them; these are named in a different way.1969

The ones that have oxygen in them are generally going to be associated with a polyatomic ion: notice, this is sulfate; this is chlorate; this SO3 is sulfite; this NO3 is nitrate.1975

You might have HNO2; this is called nitrite.1989

OK, here is how these are named.1995

You don't use the hydro- any time you have an acid that has oxygen in it.2000

This is just the root of the element that makes up the polyatomic ion, and if the name ends in -ate--if a polyatomic ion name ends in -ate--you use the -ic ending; if the polyatomic ion name ends in -ite, you use the -ous ending.2004

This one would actually be called sulfuric acid.2030

Again, it's just a balance of charge: SO4 is just 2-; H is +1; that is why you have 2 hydrogens.2039

That is all you are doing: you need to still balance the charge--this is still treated like an ionic compound.2048

This is sulfuric acid; well, if I look up ClO3, that is chlorate; it ends in -ate, so the -ate becomes -ic; so it becomes chloric acid.2053

This one, SO3, is sulfite; therefore, this becomes sulfurous acid (remember, if it ends in -ite, the -ite changes to -ous; if it ends in -ate, it ends in -ic).2067

Anything with an oxygen in it does not have the hydro- prefix.2082

This right here is nitric acid, because it's from nitrate.2087

This HNO2...NO2 is nitrite; therefore, this is nitrous acid.2095

That's it; that is how acids are named.2106

This is going from symbol to name; if we go the other way around...let's say, for example, you had something like chlorous acid.2108

Chlorous acid...well, this -ous ending is telling me that I am dealing with a chlorite anion; therefore--I know chlorite is ClO2-, so--I know that H is +1; they balance; so the symbol for this is HClO2; that's it.2122

Let's do a couple more: let's say if we said...how about chromic acid?2146

Chromic acid: well, it ends in -ic, so it comes from a polyatomic ion that ends in -ate; as it turns out, it is chromate, CrO4.2155

It is 2-; well, H is +1; how many H's do we need to balance the 2- charge? We need 2 of them.2166

So, the symbol is H2CrO4; that's it.2173

Let's say you had something like...how about phosphoric acid?2182

Phosphoric acid: well, phosphoric acid ends in -ic, so we know that we're dealing with the phosphate anion.2191

The phosphate anion is a 3- charge; H is a +1 charge; so I need 3 of these: H3PO4.2200

That is the symbol for phosphoric acid.2209

OK, so now we have talked about how to name compounds, how to go from the symbol to the name and from the name to the symbol.2211

This is going to be, of course, ubiquitous throughout the course.2217

You absolutely have to be able to understand how to name the compounds.2221

On the AP exam, sometimes the symbol will be given; often, in the free response section, the symbol will not be given.2225

You have to come up with the symbol--not only the symbol, but you have to come up with the equation; in fact, one of the last sections of the free response is a series of reactions, and they're just going to give you the names.2232

They're going to say, "This reacts with this; what happens?"; you have to know the symbol and you have to know the reaction; so naming--if you can't do naming, unfortunately, nothing else will work...so there is that.2246

OK, so I'm going to close off this discussion with a problem in percent composition.2258

Again, this is sort of just a general review of the basic techniques of chemistry, that I'm just going to go over quickly.2264

One sort of standard problem is percent composition; in other words, if I have some compound, like C6H12O6, which is glucose, what percentage of it, by mass, is carbon? What percentage of it is hydrogen? What percentage of it is oxygen?2270

I'm just going to do one of those problems, just so you see the general process--as a review.2289

Percent composition by mass (and generally, they'll be talking about mass; if they talk about anything else, they'll specify what they mean): OK, so calculate the percent composition of each element in Mg(NO3)2.2297

This is magnesium nitrate.2335

Well, let's see what we have.2339

We need...basically, when we are calculating percent composition--as you know, a percent is a part over the whole, so we're going to take the mass of magnesium over the whole, the mass of nitrogen over the whole, and the mass of oxygen over the whole.2344

Let's see what we have: magnesium is 24.31 grams per mole, and then we have 2 nitrogens--that comes to 28.02 grams per mole (and a gram per mole is the unit of molar mass, which I'm hoping you're familiar with), and 6 oxygens gives us 96 grams per mole.2358

OK, so the total mass is going to be 148.33 grams; therefore, the percent magnesium is equal to 2431 divided by 148.33, times 100, and you end up with 16.39%.2388

That means, of this 148.33 grams, about 16 or 16 and a half percent of it is magnesium; that is all that means.2420

Percent nitrogen: it equals 28.02 divided by 148.33, times 100, and you end up with 18.89%.2428

That means, of that mass, about 19% of it is nitrogen.2445

Then, the percent oxygen; you can either calculate it, or you can just add these two and subtract from 100; and you're going to get the same answer.2449

96 divided by 148.33, times 100...and you end up with 64.72%.2459

So, in magnesium nitrate, the majority of the mass is actually occupied by oxygen.2470

OK, thank you for joining us here at Educator.com for our first lesson of AP Chemistry.2478

We'll see you next time; goodbye.2482