Can you explain the composition of carbonate?

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In summary: Ionic and covalent bonds both involve losing or gaining electrons, but ionic bonds are usually weaker and covalent bonds are usually stronger.
  • #1
scott_alexsk
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What are the monoatomic ions or elements( I am not sure anymore) that make up carbonate? Once this is answered I can ask my real question.
-Scott
 
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  • #2
Carbonate is CO3 with a -2 charge on the ion.
 
  • #3
Knowing what monoatomic ions that make up the carbonate allows me to settle a dispute I have had with several people. Orginally my teacher said that the atoms making up the carbonate were all neutral. I had a feeling they were monoatomic ions involved. Now that I know this do monoatomic ions occur naturally in nature and if so how do they occur and are they stable? I mean how would carbonate come to be. From what elements would oxygen be able to take a single electron, then in another reaction bond with carbon?
Thanks for your help so far.
-Scott (Hey who deleted that last guys post that I just responded to?)
 
  • #4
the atoms making up the Carbonare ion (Carbon and 3 Oxygens), are not necesarily held together ionicly. The Ion as a whole has a charge, but the individual components of the ion can be held together covalently by sharing electrons.

Monoatomic ions can occur however.
Quite often in the alkili or alkiline Earth elements will form cations (+), and the halogens and the "chalcogens" (I think that is their name) will form -2 charges. Transition metals can form all sorts of different charges.
Take this compound for instance,
Iron (III) Oxide, Fe2O3,
the Iron has a +3 charge, the Oxygen has a -2.
or Sodium Chloride, NaCl
Sodium has a +1 charge, Chlorine has a -1 charge.
Or in [acidic] water, the Hydronium ion will form, which can be written as H3O+1 or H+
 
  • #5
mrjeffy321 said:
the atoms making up the Carbonare ion (Carbon and 3 Oxygens), are not necesarily held together ionicly. The Ion as a whole has a charge, but the individual components of the ion can be held together covalently by sharing electrons.
Even covalent bonds have some polarity (or ionic character) and hence there can be partial charge held by different atoms of the radical. In the carbonate radical, most of the 2- charge is held by two of the three O-atoms (the two that are single-bonded to the C-atom.
 
  • #6
scott_alexsk said:
Knowing what monoatomic ions that make up the carbonate allows me to settle a dispute I have had with several people. Orginally my teacher said that the atoms making up the carbonate were all neutral. I had a feeling they were monoatomic ions involved. Now that I know this do monoatomic ions occur naturally in nature and if so how do they occur and are they stable? I mean how would carbonate come to be. From what elements would oxygen be able to take a single electron, then in another reaction bond with carbon?

Carbonate is actually a resonsance structure. If you draw a lewis structure, you would have it so one of the oxygens is double bonded, and two the oxygens are single bonded and able to make one bond each. The lewis structure does the job for all intents and purposes, but it's technically incorrect. The charge isn't held by any specific oxygen(s), but it's shared among the three of them.
I would conclude that monoatomic ions are not involved, but that's just my opinion.

As for the monoatomic ions and their stability, no they do not exist. You'll never find carbon with a +4 charge as an ion; that just won't happen. You also won't find oxygen as 2-. All metal oxides are bases as soon as they touch water, and all nonmetal oxides are acids when they touch water; remember that water is almost everywhere, even in the air.
CaO + H2O --> Ca(OH)2 the OH does not break apart, so the O isn't a standalone ion
CO2 + H2O --> H2CO3 the O's stay as part of the resonance structure of CO3, still no standalone O ions
 
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  • #7
There is the reason I asked the question in the first place. There has been such a contraversy over what the simple composing elements/ions that make up carbonate. With someone finally agreeing with what my chemistry teacher said, how can the bonded elements have a charge in this structure? I mean what allows bonded nuetral atoms to become not nuetral?
-Scott
 
  • #8
I'm not really sure I'm interpreting your question correctly but I'll try.

Ionic and covalent bonds are basically the same thing, but the terms themselves represent how things dissociate. Take something like NaCl. Na loses an electron, Cl gains an electron. The Na has a very weak attraction to the electrons, so it just accepts defeat and leaves the electrons to Cl. NaCl isn't even a molecule; it's just a ratio between atoms. Now look at something like CO2. O takes electrons from the C, but the C still holds onto those electrons; it's like a tug of war. Since the carbon and oxygen never really separate, you can't say that either has an official charge, but you can definitely say the oxygen is negative compared to the carbon because it can hold the electrons tighter than carbon can. Now throw that CO2 into water and you get H2CO3 (just slap a water on). H2CO3 does exist as a single molecule, but it has a dissociation constant tied to it. The hydrogens are bound to the oxygens, and as you know, oxygen has a much tighter grip on the elctrons than hydrogen does. Hydrogen just goes away without its electron leaving HCO3- and H+. This molecule also has a dissociation constant. Another hydrogen can leave, again without an electron because oxygen stole it, to get CO3-2 and another H+.
The negative charge is just there to show that the source of those electrons is no longer joined to the carbonate :biggrin:
 
  • #9
So as a result of the shared electrons within the polyatomic ions, the charge is not completely balanced and that produces a negative two charge in carbonate, right? I understand what you are saying about polarization within nuetral molocuels, but what makes these molocuels different than polyatomic ions which have a charge?
-Scott
 
  • #10
If you have neutral atoms coming together and bonding, no matter how disproportional the "share factor" is between them, the overall molecule will be neutral. However, in some cases, take Carbon Monoxide (CO) for instance, even though the overall molecule is neutral, the Oxygen develops a slight negative charge and the Carbon gets a slight positive charge due to the Oxygen pulling the electrons more towards its side of the molecule.
In some cases, one atom pulls so hard on the electrons of another atom, we say that it was completely removed from the original atom and added to the second atom. In this case, you have an ionic bond. So take Sodium (Na) and Chlorine (Cl), when these two react, the Chlorine takes an electron away from the Sodium to make Na+ and Cl-, which form an overall neutral ionic compound NaCl. Bonds can be considered partially covalent and partially ionic, since the electron is still technically shared between the two atoms by a certain percentage of the time.

The way a compound would get an overall charge is if it either gains or looses electrons to something else. For instance the Carbonate ion has a -2 charge; this is not because of any polarity in bonds inside the compound, but because it has an extra 2 electron.
 
  • #11
There is the problem. Some people like my chemistry teacher say that there are simply just elements making up these charged structures while others say that there are monoatomic ions making up the element. Repeatedly I have been told by reliable sources that the elements are perfectly neutral but to some structure unknown to me they can have a negative charge overall even though there are no additional electrons. Everyone here seems to have the same problem with answering this question.
-Scott
 
  • #12
scott_alexsk said:
There is the problem. Some people like my chemistry teacher say that there are simply just elements making up these charged structures while others say that there are monoatomic ions making up the element. Repeatedly I have been told by reliable sources that the elements are perfectly neutral but to some structure unknown to me they can have a negative charge overall even though there are no additional electrons. Everyone here seems to have the same problem with answering this question.
-Scott
The problem with this "discussion" is that the question really makes no sense to the responders and they are trying their best to interpret it in some manner that allows explanation. Scott, either you are wording your posts very poorly, or you are missing key concepts in your understanding.

It makes no sense at to say for instance "there are simply just elements making up these charged structures" or to say "there are monoatomic ions making up the element". This is just - to say it bluntly - gibberish.

You are confusing concepts like element, compound, molecule, atom, ion and radical. Please revise all these concepts, then go over the chapter that deals with Lewis structures. That should clear up any confusion you have.

There has been such a contraversy over what the simple composing elements/ions that make up carbonate.
This may be news to you, but there is NO controversy. It's possible that your chemistry teacher has a poor understanding of the concepts as well, but that's as far any controversy here goes.

Related thread : https://www.physicsforums.com/showthread.php?t=97543
 
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  • #13
That was very stupid of me. I apologize for wasting your time. Nevertheless it seems that there is a contradiction Gukul. ShawnD, my Chemistry teacher, and a college student I talked to all say that monatomic ions are not involved in the structure of the polyatomic ion carbonate. My chemistry teacher atleast said that the way the electrons are bonded allows for a prevailing negative charge because of the way the electrons are postioned in the bond. My orginal question was intended to try to understand what reasoning there is behind their answer but I got tied up in the red tape of the compostite radicals or elements of carbonate. I might as well ask what a resonance structure is because that might have something to do with it and may help in my understanding of the problem.
-Scott
 
  • #14
scott_alexsk said:
I might as well ask what a resonance structure is because that might have something to do with it and may help in my understanding of the problem.
As Gokul suggested, it might be a good idea to review your Lewis dot diagrams :wink:

Anyway, on with resonance:
Let's take carbonate as an example. To represent its structure--i.e., one of three major resonance forms---you would draw one carbon atom surrounded by three atoms of oxygen. (As it stands, a carbonate molecule [tex]\text{CO}_3 \, ^{2-}[/tex] is comprised of one atom of carbon along with three atoms of oxygen)

As you know, carbon is most likely (unless you deal with carbocations and carboanions, like I did when I took Organic Chemistry :smile:) to have a neutral formal charge--->i.e., a formal charge of zero. (You can review formal charge http://www.westga.edu/~chem/courses/chem1212slattery/contents/chapter8-all/img031.gif [Broken]. It will help you construct your Lewis dot diagrams.)

Also, as you know, carbon has four valence electrons, and does not generally have lone pairs. Therefore, for the formal carbon charge to be zero, it must share 8 electrons.

However, carbonate is [tex]\text{CO}_3 \, ^{2-}[/tex], and therefore the atom of carbon must share 8 electrons with 3 oxygen atoms. What this means: two electrons will remain delocalized!

You see, no oxygen atom has a "specific priority" over the other oxygen atoms to receive these two electrons. Thus, you cannot form a localized double-bond. Those two delocalized electrons can exist any carbon-oxygen bond in carbonate!

And thus, we can draw three major resonance forms----->constantly transferring the "double bond" to a different oxygen each time we draw another such resonance structure.

And, due to those two delocalized electrons, we have an overall -2 charge for the carbonate molecule. Hence the term, "polyatomic" ion. Basically, you have carbonate anion.
---------------------------------------------------------------------
Now back your previous responses:

While carbonate has an overall -2 charge, oxygen is much more electronegative than carbon. Therefore, you will find that the two delocalized electrons will primarily/mainly exist around the oxygen atoms---->to give any two of the oxygen atoms a [tex](\delta ^{-} )[/tex]|->i.e., a partial negative.

You see, the carbon--oxygen bond is "polar covalent". While oxygen is more electronegative than carbon, the relative difference in electronegativity is too small to be pronounced "ionic". However, each major resonance structure will show two oxygens with an additional electron--->therefore, you might observe the oxygen atoms to possesses -1 charge each. (Two of these oxygen anions will develop the overall -2 charge for the carbonate molecule).

Thus, we might say carbonate has two monoatomic oxygen ions in each of its distinct major resonance forms.

However, as ShawnD and I pointed out earlier, no oxygen or group of oxygens has a "specific priority" over the two delocalized electrons. Thus, no major resonance form will have a "specific priority" over the other major resonance forms.

Hope this helps! :smile:
 
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  • #15
I really appreciate that and I think I get it. So even though the atoms making up the element are nuetral because of the dislocalization of the double bond, the prevailing outside charge is -2. Now I think I understand this, but why should the electrons cause a prevailng -2 charge? I mean how does the postion of the double bond electrons with all three oxygens create this charge? How are they postioned to escape the postive charge of the protons? Also is this true with all double bonds in nature (ie similar situation, different atoms)?
 
  • #16
I really appreciate that and I think I get it. So even though the atoms making up the element are nuetral because of the dislocalization of the double bond, the prevailing outside charge is -2.

You must see that the atoms can't be both charged and neutral at the same time. The carbonate ion is charged due to it having 2 extra electrons - no amount of double bond moving will remove this charge.

The part I think you are missing is -This polyatomic ion has picked up 2 electrons from the breaking of two bonds in which 2 +ve ions were released and the electrons from the bonds were wholly retained on the oxygen’s.

Resonance will probably only confuse the problem but with this ion we would use resonance to show that there are more than one ways of arranging the -ve charges, this has more to do with ion stability and structure than trying to understand overall charge.

Now I think I understand this, but why should the electrons cause a prevailng -2 charge? I mean how does the postion of the double bond electrons with all three oxygens create this charge? How are they postioned to escape the postive charge of the protons? Also is this true with all double bonds in nature (ie similar situation, different atoms)?

There is a conservation of charge law that needs to be obeyed - No matter how exotic your resonance form looks or how much you move a double bond around if you start with a -2 charged molecule you must end up with a -2 charged molecule; if you don’t a chemical reaction has occurred.

Resonance is a tricky thing which you should not rush into until you need to.

Hope I helped o:) o:)
 
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  • #17
I thought that the first explanation sounded werid anyways. So how does the carbonate get the -2 charge? Is it that there are monoatomic ions making up carbonate, if so which, or does it gain electrons from a different source?
-Scott
 
  • #18
LordofBaal said:
You must see that the atoms can't be both charged and neutral at the same time. The carbonate ion is charged due to it having 2 extra electrons - no amount of double bond moving will remove this charge.
scott_alexsk said:
I thought that the first explanation sounded werid anyways. So how does the carbonate get the -2 charge? Is it that there are monoatomic ions making up carbonate, if so which, or does it gain electrons from a different source?
-Scott

Conservation of charge, how's that difficult to understand? :bugeye:
 
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  • #19
scott_alexsk said:
I thought that the first explanation sounded werid anyways. So how does the carbonate get the -2 charge? Is it that there are monoatomic ions making up carbonate, if so which, or does it gain electrons from a different source?
-Scott
If the ions were monoatomic, they wouldn't be polyatomic. Carbonate is polyatomic :smile:
 
  • #20
"I would conclude that monoatomic ions are not involved, but that's just my opinion."-ShawnD
Now that I am certain that carbonate has 2 more electrons than protons, hence the negative two charge, in what way does it obtain these electrons? Is it that it forms bonds with two monoatomic oxygen ions with a negative 1 charge, each, or is it something else as ShawnD suggests. How would carbonate gain electrons in your opinion? It is clear to me that it cannot simply just magically take electrons from another atom and remain unbonded, if Gukul and the others are incorrect, how do you justify your prior response ShawnD? I should have made myself more clear my prior post.
-Scott
 
  • #21
scott_alexsk said:
It is clear to me that it cannot simply just magically take electrons from another atom and remain unbonded
That's exactly what happens.
 
  • #22
So I am incorrect?
-Scott
 
  • #23
I'm not really sure if you're correct (still a bit confused here).

A friend suggested to me that you might be thinking of oxidation states. In that case, carbon is +4 and each oxygen is -2. Carbonate has 1 carbon and 3 oxygens so it's +4 -2(3) = official charge of -2. Does that help?
 
  • #24
The reason I started this thread in the first place, was because when I asked my chemistry teacher how polyatomic ions formed with a charge, but without being bonded to some other atom, she gave me a strange answer. I mean what element does carbonate get the 2- from? It cannot just steal the electrons from nothing, there has to be some other element it gets these electrons from. Also where does carbonate occur in nature? My chemistry teacher gave me a werid answer that it does not gain any extra electrons, but it becomes a prevailing negative 2 charge because of the bonds. Basically it seems that everyone here has defeated that argument (repeatedly), so how does carbonate occur? What chemical reactions form it and how common is it?
Thanks,
-Scott
 
  • #25
Carbonates are very common in nature. Calcium carbonate is the main component of limestone, which makes up about 10% of all sedimentary rock.

Carbonates make up a whole class of minerals as well, see http://en.wikipedia.org/wiki/Carbonate_minerals

When carbon dioxide from the atmosphere dissolves in water, a dilute solution of carbonic acid is formed. That's why natural (not acid rain) rainwater is slightly acidic (pH of around 6). The carbonic acid then slowly leaches rocks, forming carbonates.
 
  • #26
scott_alexsk said:
so how does carbonate occur? What chemical reactions form it and how common is it?
I answered that one the first page, but I'll make it more readable.

Start with CO2
Add water to get H2CO3
A hydrogen leaves to get H+ and HCO3-
Another hydrogen leaves to get 2H+ and CO3--

It's a very common reaction. It's why pop tastes better when it's not flat.
 
  • #27
bomba923 said:
[tex]\begin{gathered}
{\text{CO}}_2 \left( g \right) + {\text{H}}_2 {\text{O}}\left( \ell \right) \rightleftharpoons {\text{H}}_2 {\text{CO}}_3 \hfill \\
{\text{H}}_2 {\text{CO}}_3 + {\text{H}}_2 {\text{O}} \rightleftharpoons {\text{H}}_3 {\text{O}}^ + + {{\text{HCO}}_3} ^ - \hfill \\
{{\text{HCO}}_3} ^ - + {\text{H}}_2 {\text{O}} \rightleftharpoons {\text{H}}_3 {\text{O}}^ + + {{\text{CO}}_3} ^{2 - } \hfill \\
\end{gathered} [/tex]
This series of equilibrium reactions is one of the buffer systems in every mamal on the planet. :smile:
 
  • #28
Thanks guys, I finally was able to get that cleared up. I appreciate your time.
-Scott
 
  • #29
You must see that the atoms can't be both charged and neutral at the same time. The carbonate ion is charged due to it having 2 extra electrons - no amount of double bond moving will remove this charge.

OK. I am resurrecting this thread. I have found that my own book directly contradicts LordOfBaals 'conservation charge'. It lists the first example of a polyatomic ion as being hydroxide.

The oxygen atom is bonded covalently to the hydrogean atom. The hydrogean atom is stable with two electrons in its outer level. The hydrogean atom contributes only one electron to the octet of oxygen. The other electron required for oxygen to have a stable octet is the one that gives the -1 charge to the ion.

Unless this has changed since 1998, you guys are wrong. I would appreciate someone responding who actually knows what he or she is talking about. To reitterate, my question is "How can there be a charge
if there is a equal number of protons and electrons, in a polyatomic ion?"
-Scott:mad:
 
  • #30
i think all this polyatomic this and mono atomic that has prevented a lot of readers from understanding what you are looking for.

Hydroxide is indeed a 'polyatomic' ion - I usually call it an ion but hey.
It is comprised of a hydrogen atom and an oxygen atom that has 1 extra electron - that gives it the 1- charge
does this picture help you get it?
 

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  • #31
scott_alexsk said:
I would appreciate someone responding who actually knows what he or she is talking about. To reitterate, my question is "How can there be a charge
if there is a equal number of protons and electrons, in a polyatomic ion?"
-Scott:mad:
To think that the people who have responded don't know what they are talking about is just wrong, some a quite knowledgeable (and it is best not to push people away that are trying to help).

As LordOfBaal said,
You must see that the atoms can't be both charged and neutral at the same time. The carbonate ion is charged due to it having 2 extra electrons - no amount of double bond moving will remove this charge.
This is inline with your book, saying that the Hydroxide ion (and more specifically, the Oxygen side of the Hydroxide) picked up an extra electron.
When the extra electron is picked up (or lost), the number of protons and electrons are not equal, and there is an imbalance in the charge. In Hydroxide's case, there is a -1 charge.
 
  • #32
Sorry about that. You guys explained it. Its just that when I have looked at the diagrams that model polyatomic ions before, I couldn't tell the number of electrons in the model, because for extra electrons would be marked with a 'X'. I didn't know this counted as an electron. Just to let you know, your explanations always made sense, but I thought that there was more information I was not getting.
Thanks and sorry,
-Scott
 

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