# Determining the names of Ionic Compounds from their formulas

#### opus

Gold Member
1. The problem statement, all variables and given/known data

Name the ionic compounds:

a) $K_2SO_4$

b) $Ba(OH)_2$

c) $FeCl_3$

2. Relevant equations

3. The attempt at a solution

These problems are actually in a sample exercise so I already have the answers, I just am really lost in this section of chemical nomenclature.

First, at the start of the problem, the text states that "In naming ionic compounds, it is important to recognize polyatomic ions and to determine the charge of cations with variable charge."

I am lost at the bold statement.

What I do know is that polyatomic ions are molecules with a net charge, meaning the number of electrons and protons of the molecule as a whole are not equal.
I also know that cations are elements that have lost an electron (typically metals) and have thus taken on a positive charge. I also know that some cations can take on different levels of positive charge (ie, losing more than one electron). But I don't quite understand what to do with this information to answer the given questions.

Any tips on what I should be looking for to answer these questions?

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#### symbolipoint

Homework Helper
Gold Member
No confusion should occur in those expected names.

(a)
Potassium sulfate

(b)
Barium hydroxide

(c)
Ferric chloride

Why "ferric" and not "ferrous"?
Fe+2, ferrous
Fe+3, ferric

#### opus

Gold Member
No confusion should occur in those expected names.
I suppose I'll rephrase my question.
I'm new to Chemistry. I've stated what I know about the subject matter, and I'm asking what I should be looking for in the given formulas relating to the bolded part of the post. As stated, I have the answers to the questions. I just don't know how they were obtained, so there is confusion. That is the purpose of the thread- to hopefully clear up my confusion. Any enlightenment on the matter would be greatly appreciated.

#### symbolipoint

Homework Helper
Gold Member
I suppose I'll rephrase my question.
I'm new to Chemistry. I've stated what I know about the subject matter, and I'm asking what I should be looking for in the given formulas relating to the bolded part of the post. As stated, I have the answers to the questions. I just don't know how they were obtained, so there is confusion. That is the purpose of the thread- to hopefully clear up my confusion. Any enlightenment on the matter would be greatly appreciated.
No relevant equations. You just learn and then recognize the inorganic ions, both when symbolized not in a compound formula, and when symbolized in a compound formula. This is a combination of concept understanding and some memorizing. You both learn to recognize the ion and its name.

Attempt at Solution is you try to give the name and explain your justification for what you decided.

As you have also bolded, you LEARN TO RECOGNIZE the ion, and its expected ionic charge. You are also given much guidance about the Periodic Table of Elements to make a good decision on many expected charges for some or several common ions.

Here is a little bit of guided thinking:
BaSO4
"Barium Sulfate"
Why one unit of Barium? Look where you find this element in the Periodic Table. What charge would you guess the ION of Barium would have?

If that is not all you could do, you should recognize the sulfate ion . You should learn and them have memorized, charge of sulfate is minu 2.
Remember or found yet what is the charge for the Barium ion? Formula here shows 1 Barium ion and 1 sulfate ion. Need to balance the charges. +2+(-2)=0.

1 Ba+2 and 1 SO4-2 makes the one unit of BaSO4.

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#### opus

Gold Member
Ok that makes more sense, thank you. In my text it states that there are "over 50 million different substances (or compounds, I forget which it was)". And the text went to great length to go over the naming conventions of things like oxyanions, etc but it was extremely confusing- really about 4 pages of just rules and none of it seemed to have any rhyme or reason For example, it went over the terms "ferrous" and "ferric" but then followed by saying to use roman numerals instead and listed more than two (so why only ferrous and ferric if their equivalence is of roman numerals which go past 2?). So it seemed like memorization was virtually impossible with these things and I should be able to derive everything. So you're saying that with the periodic table, and a handful or memorized ions, I should be okay for now?
This topic is really confusing and I think I'm going to have to have a face-to-face with my professor for a discussion on it. After going over the rules again, I don't think it would be effective to ask over a forum so I should have refrained. I don't have a good enough understanding to narrow my questions down. Thank you though for taking the time to write all that out!

#### symbolipoint

Homework Helper
Gold Member
Ok that makes more sense, thank you. In my text it states that there are "over 50 million different substances (or compounds, I forget which it was)". And the text went to great length to go over the naming conventions of things like oxyanions, etc but it was extremely confusing- really about 4 pages of just rules and none of it seemed to have any rhyme or reason For example, it went over the terms "ferrous" and "ferric" but then followed by saying to use roman numerals instead and listed more than two (so why only ferrous and ferric if their equivalence is of roman numerals which go past 2?). So it seemed like memorization was virtually impossible with these things and I should be able to derive everything. So you're saying that with the periodic table, and a handful or memorized ions, I should be okay for now?
This topic is really confusing and I think I'm going to have to have a face-to-face with my professor for a discussion on it. After going over the rules again, I don't think it would be effective to ask over a forum so I should have refrained. I don't have a good enough understanding to narrow my questions down. Thank you though for taking the time to write all that out!
Introductory and Elementary Chemistry as was taught and studied so very many years ago was not too confusing for most people. Maybe textbooks have changed in recent years? But I have not seen any for many many years now. opus, we/I not know how much of Chemistry you have studied already. This must be your first course - just a guess. Are you much better at Mathematics and Physics?

A couple of good books from the past were of authors Morten? or Mortenson? Mortimer, and Petrucci. These authors wrote some General Chemistry textbooks. Elementary and Introductory books should be a little bit easier to learn from.

#### opus

Gold Member
Introductory and Elementary Chemistry as was taught and studied so very many years ago was not too confusing for most people. Maybe textbooks have changed in recent years? But I have not seen any for many many years now. opus, we/I not know how much of Chemistry you have studied already. This must be your first course - just a guess. Are you much better at Mathematics and Physics?

A couple of good books from the past were of authors Morten? or Mortenson? Mortimer, and Petrucci. These authors wrote some General Chemistry textbooks. Elementary and Introductory books should be a little bit easier to learn from.
This is my first chemistry class but I do like the book a lot. The rest of the material is great and it makes a lot of sense (although only on chapter 3 so far, but so far I love it). I understand the concept of charges and bonding, etc, but the nomenclature seems so messy that it's hard to get a hold of it.
As for mathematics, I feel pretty solid so far on it. I'm only in Calculus I, but I took Trigonometry and College Algebra over the summer and ended with a 98% in each and Calculus so far is challenging but really interesting and I love it.
I haven't taken physics yet because I thought it would be good to have a semester of calculus under my belt, so that will be next semester.

#### symbolipoint

Homework Helper
Gold Member
opus, you might change. You will at least find that later study of Chemistry will use some Mathematics, mostly up to Intermediate Algebra, and a sprinkling of other things. Regarding the nomenclature in Chemistry, you will become accustomed to it.

Look at the article https://en.wikipedia.org/wiki/Oxyacid for some extra reading. See the section on oxyacids, and try to learn from the listed sulfur anions with oxygen atoms. This may help with learning some of the names.

#### opus

Gold Member
Yeah I think I just need to have a face to face conversation about the nomenclature so I can bombard my professor with questions and identify where my misunderstandings are. Then once I get that down I can make a post about specific questions. Really looking forward to using some math on this stuff though! We did some dimensional analysis which was basic but really fun and interesting. Thanks for your suggestions and for taking the time to post!

#### Borek

Mentor
Nomenclature is confusing because it mixes systematic approach with a lot of old conventions - and you need to know the old conventions as they are still used here and there. Ferrous/ferric is a thing of the past and was replaced by Fe(II) and Fe(III) partially because it was too limited (which is exactly what you are concerned about).

#### opus

Gold Member
Thanks Borek. After watching a few videos of people doing it, it's a lot easier than I had originally thought (seeing it done it a book didn't make sense at all). I think now that I've come to the understanding that there are certain polyatomic ions that should be memorized like symbolipoint said, and using the periodic table with the understanding of a) elements want to lose or gain electrons to be stable, and b) their position on the table depends on if they'll lose or gain and how many, makes more sense now.

For example in the first question, $K$ is in column 1 and will lose an electron to take on a positive 1 charge. $SO_4$ is a polyatomic ion with charge of minus 2. So for these two to bond, there would need to be two K's for the one polyatomic ion.

So checking if a chemical formula makes some sense now, it's the verbage that is wirey. I'll just have to keep doing practice problems!

"Determining the names of Ionic Compounds from their formulas"

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