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Thread: Chemical Bonding & Reactions

  1. #1 Chemical Bonding & Reactions 
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    First off,

    Is the act of bonding always a reaction? And does the act of reaction always lead to bonding?

    My intuition tells me that a reaction MUST either create a compound or break a compound apart into elements, and that there is no chemical reaction without this creation or destruction of bonds.

    How does that sound?

    Secondly, I have some inquires about 'chemical equation/notation'


    Does the presentation of the equation differ depending on the type of chemical bonding taking place(ionic, covalent, etc)?

    Can the same two elements bond in two different ways?

    Or do specific types of bonding apply to specific combinations of elements, and vice versa?


    I'm aware of that there are two major types of bonds:

    Intramolecular Bonds – Strong
    (Bonds within the molecule)

    Covalent Bonds
    Ionic Bonds
    Metallic Bonds

    Intermolecular Bonds - Weak
    (Bonds between molecules)

    Hydrogen Bonds
    Van der Waals Forces
    Molecule-Ion Attractions


    I'm basically just wondering if strong and weak bonds occur only among certain types of elements.


    Thanks.


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    You ask some provocative questions. Let me see what I can do.

    Is the act of bonding always a reaction? And does the act of reaction always lead to bonding?
    Consider graphite subjected to intense heat and pressure, forming diamond. Bonds must be broken and reformed, but is this a chemical reaction? I'd say no. You decide.

    Does the presentation of the equation differ depending on the type of chemical bonding taking place(ionic, covalent, etc)?
    Yes, but the differences are due to the author's desire to present a certain aspect of the reaction. He may wish to simply show products/reactants of a specific reaction or he may wish to emphasize the ionic nature of the reaction, oxidation/reduction, or whatever, of the same reaction. It's up to him.

    Can the same two elements bond in two different ways?
    Certainly. That's what led John Dalton to his original atomic theory some two centuries ago. His work was based on the different nitrogen-oxygen compounds.

    I'm basically just wondering if strong and weak bonds occur only among certain types of elements.
    The strong bonds you listed form molecules, typically stable. The other bonds are physical only. They affect a system's properties but are not considered true chemical bonds.

    I hope these responses are satisfactory. Check back with further questions.


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  4. #3  
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    Steve,

    Quote Originally Posted by Steve
    Quote Originally Posted by Remit
    Is the act of bonding always a reaction? And does the act of reaction always lead to bonding?
    Consider graphite subjected to intense heat and pressure, forming diamond. Bonds must be broken and reformed, but is this a chemical reaction? I'd say no. You decide.
    Ah, I see.

    I suppose the example you gave of the graphite turning into diamond is not so different from water turning into steam or ice.

    This of course raises some questions about the sort of bonding that takes place between atoms of the same kind in general. Not something I even thought about before....

    I'm just learning the basics right now.

    What the most common type of bond?

    How do atom's of the same element, like gold, bond? When I look at a chunk of pure gold, should I be picturing an agglomeration of Gold atoms bonded to each other?

    Thanks for your replies, Steve. Hope to hear back from you again.
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    Let's deal with one question at a time. Maybe some other folk might wish to jump in with additional ideas.

    I suppose the example you gave of the graphite turning into diamond is not so different from water turning into steam or ice.
    They are quite different. The graphite/diamond example shows two allotropic forms of an element. (A third allotrope of carbon is fullerene, including the buckyball.) Allotropes involve a pure element whose atoms are bonded in different ways. Several element have various numbers of allotropic forms:

    • carbon
    • oxygen/ozone
    • sulfur
    • phosphorus
    • tin
    • plutonium

    Water changing its state retains all of its original chemical bonds as individual H2O molecules. We do, however, disrupt some of the physical forces that act on the molecules. It's not the same as allotropic forms.

    BTW, a perfect diamond crystal might be considered a single huge molecule. Another example of a giant molecule would be a synthetic rubber tire, at least before it suffers cracks and flaws from use.

    Metals have the peculiar property of forming the metallic bond, in which certain electrons are free to travel throughtout the metal crystal. Let's deal with that another day.
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    Quote Originally Posted by SteveF
    Let's deal with one question at a time. Maybe some other folk might wish to jump in with additional ideas.

    I suppose the example you gave of the graphite turning into diamond is not so different from water turning into steam or ice.
    They are quite different. The graphite/diamond example shows two allotropic forms of an element.
    Hmmm. And that of course raises some questions...

    which I think I'll postpone until I resolve an inquiry that I think is much more fundamental.

    (A third allotrope of carbon is fullerene, including the buckyball.) Allotrope's involve a pure element whose atoms are bonded in different ways. Several element have various numbers of allotropic forms:

    • carbon
    • oxygen/ozone
    • sulfur
    • phosphorus
    • tin
    • plutonium

    Water changing its state retains all of its original chemical bonds as individual H2O molecules. We do, however, disrupt some of the physical forces that act on the molecules. It's not the same as allotropic forms.

    BTW, a perfect diamond crystal might be considered a single huge molecule. Another example of a giant molecule would be a synthetic rubber tire, at least before it suffers cracks and flaws from use.

    Metals have the peculiar property of forming the metallic bond, in which certain electrons are free to travel throughtout the metal crystal. Let's deal with that another day.
    All of that I'm afraid is too advanced for me! I apologize - it must be frustrating writing all of that, and having the student say he's not ready for it. But I assure you Steve, I'll eventually come back to this allotrope business eventually.

    Until then, a much more basic inquiry emerged after I examined some basic things, and maybe you or anyone else can help me with that:

    I understand (well enough I suppose) why a single atom of oxygen, chlorine or atom is rare in nature. Since oxygen, Chlorine and hydrogen all are 1 electron short of completing their outer shells, they each tend to live as twins: (E.g, O2, H2, CL2)

    This means that the most basic chemical equations run along the lines of:

    O + O = O2
    H + H = H2
    CL + CL = CL2
    Etc, etc

    That being said, my question is:

    Is covalent bonding the most fundamental, most basic and simple type of chemical bonding?

    Also, does covalent bonding only occur between atom's of the same kind?
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    Ask away, that's why we have this forum.

    Is covalent bonding the most fundamental, most basic and simple type of chemical bonding?
    Most chemical bonds show both ionic properties and covalent properties. At the extremes we have bonds that are called purely ionic and purely covalent. Most bonds have a character that lies somewhere in between.

    The character of a chemical bond is determined to a large extent by an element's property called electronegativity, which is the strength that the nucleus tries to pull in electrons.

    In diatomic molecules, such as O2, H2, and N2, the two atoms clearly have equal electronegativity. Therefore the bonding electrons are shared equally between the two nuclei and we have a purely covalent bond.
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    Quote Originally Posted by SteveF
    Ask away, that's why we have this forum.

    Is covalent bonding the most fundamental, most basic and simple type of chemical bonding?
    Most chemical bonds show both ionic properties and covalent properties. At the extremes we have bonds that are called purely ionic and purely covalent. Most bonds have a character that lies somewhere in between.

    The character of a chemical bond is determined to a large extent by an element's property called electronegativity, which is the strength that the nucleus tries to pull in electrons.
    Right - which, if I'm not mistaken, is how we understand ionization. When the protons of the nucleus outnumber the electrons, the atom becomes a cation, a positively charged element. When the electrons outnumber the protons, we have a anion - a negatively charged element. (correct me if I'm wrong)

    In diatomic molecules, such as O2, H2, and N2, the two atoms clearly have equal electronegativity.
    Is saying they have equal electronegativity synonymous with saying the two atoms are neutral?

    Therefore the bonding electrons are shared equally between the two nuclei and we have a purely covalent bond.
    Ok, excellent. So it's nice know that all diatomic molecules are pure covalent bonds.

    How many different types of molecules are there?

    Based on my searches I found 3 major types:

    Diatomic

    * Molecules that contain two atoms.

    Homoatomic

    * Molecules that contain two or more atoms of one element.

    Hetroatomic

    * Contain at least two atoms of two or more different elements.


    ^ I'm a bit confused by the differences between Diatomic and Homoatomic. Can a Diatomic molecule be comprised of two different types of elements? How is that possible without ionization occuring? Perhaps it's not.

    If that's the case, then I guess I was wrong to say that 'all' diatomic molecules are pure covalent bonds.

    Maybe you Steve, or anyone can shed some more light on this.

    Thanks for the help so far, Steve.
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    How many different types of molecules are there?
    This is kind of just a question of semantics. There are lots of ways you can classify molecules based on their composition. Whether they are ionic or covalent is probablly the best way to look at it.

    Electronegativity aside let's look at the basics. You can think of a covalent bond as a bond between two nonmetals (doesn't matter if they are the same element or different) and an ionic bond as a bond between a metal and a nonmetal.

    In ionic bonding, the metal donates its valence electrons to give the nonmetal a full octet.

    You can think of covalent bonding as the two nonmetals sharing electrons.(This is a pretty basic understanding but it's a good place to start.)
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    You have the right idea about ions -- essentially any charged species. Incidentally, this definition can bring out one of the differences between physicists and chemists. A physicist tends to think of an ion as a charged atom; a chemist automatically assumes we are talking about a charged molecule.

    I'm a bit confused by the differences between Diatomic and Homoatomic.
    Diatomic always refers to two, exactly two atoms. It is always presumed that the two are of the same element. I suppose one can think of NaCl as diatomic, but no one ever describes it that way. What's the point?

    Homoatomic (a term you'll never see nor hear anywhere except in goofy schoolbooks) means that all the atoms of a molecule are of the same element, and can be in any number. An example is the buckyball, which consists only of sixty carbon atoms, C60.
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    Quote Originally Posted by SteveF
    I'm a bit confused by the differences between Diatomic and Homoatomic.
    Diatomic always refers to two, exactly two atoms. It is always presumed that the two are of the same element.
    According to wikipedia:

    Diatomic molecules are molecules made only of two atoms, of either the same or different chemical elements.

    Stuff on wikipedia has been wrong before, of course.

    Based on my understanding of the periodic table so far, it would seem that any diatomic molecule made of two different elements, would have to be based on an ionic bond.

    I suppose one can think of NaCl as diatomic, but no one ever describes it that way. What's the point?
    How come no one ever does? Is it because diatomic molecules are considered as only based on covalent bonds?

    NaCl is based on an ionic bond, is it not?

    BTW, in case it seems like I'm just skipping from one set of trivial facts to the next - what aiming for here, is to find a way of approaching chemical equations/notation (and chemistry in general) in a way that allows me to navigate the details with greater ease. So I guess I'm looking to grasp all the most basic general truths, as I deem this will make it easier to get clear about the details. For instance, based on the little bit of general knowledge I have about ionization, I have reasons to treat NaCl different than O2. Both may be diatomic; however, the former molecule I realize MUST be based on a different process of bonding than the later. Or am I lost?

    I figured I'd let you know that, just so it doesn't seem like I'm haphazardly jumping around without any defined aim. But maybe I'm suffering some sort of fundamental misunderstanding, which is causing me to indulge in all sorts of needless inquires. Any advice about how to approach chemistry most effectively and efficiently, I'd be grateful to hear.

    If there's any books you have found particularly helpful, by all means, let me know.

    Regards,

    Remit
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    Quote Originally Posted by rancidchickn
    How many different types of molecules are there?
    This is kind of just a question of semantics. There are lots of ways you can classify molecules based on their composition. Whether they are ionic or covalent is probably the best way to look at it.
    Ok, cool.

    Electronegativity aside let's look at the basics. You can think of a covalent bond as a bond between two nonmetals (doesn't matter if they are the same element or different)
    Is it helpful to know the most common, naturally occuring covalent bonds? How many different types of molecules are there which are based on covalent bonds?

    and an ionic bond as a bond between a metal and a nonmetal.
    Are molecules based on ionic bonds less common in the universe than molecules based on covalent bonds?

    In ionic bonding, the metal donates its valence electrons to give the nonmetal a full octet.
    And thus the nonmetal becomes an anion, while the metal becomes a cation?
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    Is it helpful to know the most common, naturally occuring covalent bonds? How many different types of molecules are there which are based on covalent bonds?
    I don't think its really helpful. I mean hydrogen and carbon are two of the most common element and they usually bonds covalently, so I would guess that covalent bonds are most common.

    More importantly though let's take a look at some reactions and get you to the point where you can balance them yourself.
    Ionic:
    The easiest way to solve for the product of an ionic compound is to criss-cross the charges. So what compound do you get when Mg reacts with Cl?

    Mg has a 2+ charge. Cl has a 1- charge. The product is MgCl2. As you can see the product has a neutral charge.

    Ok so right now you've got Mg + Cl ---> MgCl2. Next step is to balance it. You need to have the same number of each reactant as each product, because all mass must be conserved. The correct equation is Mg + 2Cl ---> MgCl2.

    Covalent:
    Two atoms can usually bond covalently in a number of different ways (tons of combinations with just C and H, some common ones like propane and butane). Anyway, given reactants and a product, you can still balance the equation.

    I started to type more about covalent bonds but I think you really need to understand how electrons behave around the nucleus to fully understand what covalent molecules are like. They sure as hell don't orbit like planets do. :P

    This page will give you a basic idea of the different orbitals and how that all works. http://www.chemguide.co.uk/atoms/pro.../atomorbs.html
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    I really like what I've read so far on that web site you linked. Whoever wrote it has a very plain, simple concise way of communicating and sounds like he really cares about teaching.

    I got a big test to study for (unrelated to chemistry) so I might not be able to pick this up again until after the weekend.

    I'm looking forward to tackling the challenges you've proposed in your above post and progressing this thread further, and am grateful for the help I received so far.
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    [I'm looking forward to tackling the challenges you've proposed in your above post and progressing this thread further, and am grateful for the help I received so far.[/quote]

    I am a high school junior who is currently taking advanced chemistry. I think i may be able to answer at least some of your chemistry questions.
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    Quote Originally Posted by remit

    Based on my understanding of the periodic table so far, it would seem that any diatomic molecule made of two different elements, would have to be based on an ionic bond.
    Ummm.. I don't think so. Just about every molecule of a non-metal with a non-metal uses covalent bonds - none of the atoms have electrons to 'give away'. So carbon dioxide, nitrous oxide etc are covalent. (I'm avoiding the hydrogen based compounds simply because hydrogen has a peculiar place in the preiodic table and, under certain conditions, even has a metallic form.)
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    Quote Originally Posted by sunshinewarrio
    Quote Originally Posted by remit

    Based on my understanding of the periodic table so far, it would seem that any diatomic molecule made of two different elements, would have to be based on an ionic bond.
    Ummm.. I don't think so. Just about every molecule of a non-metal with a non-metal uses covalent bonds - none of the atoms have electrons to 'give away'. So carbon dioxide, nitrous oxide etc are covalent. (I'm avoiding the hydrogen based compounds simply because hydrogen has a peculiar place in the preiodic table and, under certain conditions, even has a metallic form.)
    I don't think so either.

    and if we're talking *diatomics* (only two atoms) carbon *monoxide* CO, would be a better example than CO2 and *nitric* oxide, NO, not *nitrous* oxide which is N2O. cyanide (CN-, toxic, great nucleophile) is another example.
    (Fe)male = male alloyed with iron for greater strength, ductility, and magnetism.
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    Loch,

    Quote Originally Posted by loch
    I am a high school junior who is currently taking advanced chemistry. I think i may be able to answer at least some of your chemistry questions.
    Cool. Hopefully I'll be able to get ahead on my studies and find some times to take this thread further. Right now I got a big English essay to write.

    I'll try to get the thread going again near the end of the week and maybe I'll hear more from you.


    PS: Hi Sunshine warrior and (Fe)male. Hopefully I'll find some time to consider your perspective. Talk to you soon, perhaps.
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    Quote Originally Posted by rancidchickn
    Is it helpful to know the most common, naturally occuring covalent bonds? How many different types of molecules are there which are based on covalent bonds?
    I don't think its really helpful. I mean hydrogen and carbon are two of the most common elements and they usually bond covalently, so I would guess that covalent bonds are most common.
    In class, we are being introduced to both 'organic chemistry and 'covalent bonding' in the same class, as if the two are very dependent on each other. The impression given so far is that ionic bonding occurs less commonly and tends to comprise substances we normally consider inorganic. [shrug]

    Quote Originally Posted by Rancidchick
    More importantly though let's take a look at some reactions and get you to the point where you can balance them yourself.

    Ionic:

    The easiest way to solve for the product of an ionic compound is to criss-cross the charges. So what compound do you get when Mg reacts with Cl?

    Mg has a 2+ charge. Cl has a 1- charge.
    Huh? I thought an element could be charged only if it was in a bond.

    The product is MgCl2. As you can see the product has a neutral charge.
    I'm a bit confused why the elements had a charge to begin with. Are you saying that some of the elements as displayed on the periodic table are charged? I thought they were all neutral.

    Ok so right now you've got Mg + Cl ---> MgCl2. Next step is to balance it. because all mass must be conserved. The correct equation is Mg + 2Cl ---> MgCl2.
    I understand the logic, but I'm confused about how you arrived at such a premise (e.g, Cl and Mg each have a charge...).

    Quote Originally Posted by RancidChick
    Covalent:
    Two atoms can usually bond covalently in a number of different ways (tons of combinations with just C and H, some common ones like propane and butane).
    Actually, it was only a few hours ago that our teacher introduced us to 'Hydrocarbons' & 'Isomers'. Interesting stuff.
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    Quote Originally Posted by (Fe)male
    Quote Originally Posted by sunshinewarrio
    Quote Originally Posted by remit

    Based on my understanding of the periodic table so far, it would seem that any diatomic molecule made of two different elements, would have to be based on an ionic bond.
    Ummm.. I don't think so. Just about every molecule of a non-metal with a non-metal uses covalent bonds - none of the atoms have electrons to 'give away'. So carbon dioxide, nitrous oxide etc are covalent. (I'm avoiding the hydrogen based compounds simply because hydrogen has a peculiar place in the preiodic table and, under certain conditions, even has a metallic form.)
    I don't think so either.

    and if we're talking *diatomics* (only two atoms) carbon *monoxide* CO, would be a better example than CO2
    Fair enough. That being said, can carbon and oxygen combine into a diatomic ionic bond? Should I be able to determine this for my self if I understand the basics of the periodic table?

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    Quote Originally Posted by sunshinewarrio
    Quote Originally Posted by remit

    Based on my understanding of the periodic table so far, it would seem that any diatomic molecule made of two different elements, would have to be based on an ionic bond.
    Ummm.. I don't think so. Just about every molecule of a non-metal with a non-metal uses covalent bonds - none of the atoms have electrons to 'give away'. So carbon dioxide, nitrous oxide etc are covalent. (I'm avoiding the hydrogen based compounds simply because hydrogen has a peculiar place in the preiodic table and, under certain conditions, even has a metallic form.)
    Ok, fair enough. However, the examples you gave me aren't diatomic molecules, so maybe the diatomic bonds I'm referring to(comprised of only two different atoms), aren't as common as you think. I say that with all due respect, and am in no way trying to be snide.
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    In class, we are being introduced to both 'organic chemistry and 'covalent bonding' in the same class, as if the two are very dependent on each other.
    A broad definition of organic chemistry would be study of compounds containing C-H bonds. So yes, we're talking covalently bonded molecules.

    Inorganic chemistry deals with ionic solids but also covalently bonded molecules. NO2, S4N4, CO2 are all inorganic.

    I'm a bit confused why the elements had a charge to begin with. Are you saying that some of the elements as displayed on the periodic table are charged? I thought they were all neutral.
    The atoms as shown on the periodic table are in their neutral state.
    The atoms must be ions to bond though. Salt water, unlike pure water, conducts electricity because it contains ions (aka electrolytes) in solution.

    Based on my understanding of the periodic table so far, it would seem that any diatomic molecule made of two different elements, would have to be based on an ionic bond.
    Two nonmetals bonded together is a covalent bond. CO, NO, etc.
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    Hey again Steve. I hope you're still around.

    I wanted to return to something you said at the beginning of the thread:

    Quote Originally Posted by SteveF
    You ask some provocative questions. Let me see what I can do.

    Is the act of bonding always a reaction? And does the act of reaction always lead to bonding?
    Consider graphite subjected to intense heat and pressure, forming diamond. Bonds must be broken and reformed, but is this a chemical reaction? I'd say no. You decide.
    The more I think about it, the more I feel a need to be clearer about the difference between ionic and covalent bonding. The major thing I'm unclear about is the conditions which dictate whether two or more atoms form an ionic or covalent bond.

    For instance, when I consider substances like Charcoal, graphite and Diamond - - I'm not sure if they are each based on covalent bonds, of if they are all ionic, or if only one, or some of them are ionic/covalent. You know what I mean?

    I'm guessing it's only by being aware of the right conditions that we can determine or predict what type of bond comprises what.

    Am I making any sense here?
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    Quote Originally Posted by rancidchickn
    In class, we are being introduced to both 'organic chemistry and 'covalent bonding' in the same class, as if the two are very dependent on each other.
    A broad definition of organic chemistry would be study of compounds containing C-H bonds. So yes, we're talking covalently bonded molecules.
    Really. That surprises me. I would have thought there to be more compounds classified as organic, other than hydrocarbons.

    Inorganic chemistry deals with ionic solids but also covalently bonded molecules. NO2, S4N4, CO2 are all inorganic.
    Right on.


    I'm a bit confused why the elements had a charge to begin with. Are you saying that some of the elements as displayed on the periodic table are charged? I thought they were all neutral.
    The atoms as shown on the periodic table are in their neutral state.
    The atoms must be ions to bond though.
    I'm not sure what you mean. My understanding is that an atom can start off neutral and become ionized by making contact with the right kind of atom.

    How about we go back to your previous example of two Mg cations and one Cl anion.

    Before Mg combines with Cl, is it by logical necessity bonded with something else? Likewise, before Cl combines with MG, is it by logical necessity bonded with something else.

    It sounds as if there are two ways ionization can occur.

    1) Two neutral atoms come in contact with each other and form an ionic bond.

    2) Two pairs of ionized molecules meet up with each other and swap partners much like two husbands might agree to trade wives, that is, assuming the wives were also interested in trading husbands.
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    For instance, when I consider substances like Charcoal, graphite and Diamond - - I'm not sure if they are each based on covalent bonds, of if they are all ionic, or if only one, or some of them are ionic/covalent. You know what I mean?
    Ionic bonds occur between a metal ion and a nonmetal ion. That's not the case with these 3 substances.

    Coal (amorphous carbon) - the carbon atoms aren't actually bonded to each other.

    Graphite- rings of 6 carbons bonded to form sheets. The bonding that holds the carbons in this arrangement is very strong because of delocalized electrons. London dispersion force holds one sheet of graphite to the sheet below it for example. This is a weak force. That's why graphite flakes easily and we can write with it.

    Diamond- carbon tetrahedrally bonded to one another. This is what gives diamond it's hardness.

    If you want to do some reading, I would look into molecular geometry. It will help you understand why covalent molecules behave the way they do.
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    Yeah, remit, Steve is still here but lurking. I'm giving everyone else a chance to throw in their 2 cents worth.

    The more I think about it, the more I feel a need to be clearer about the difference between ionic and covalent bonding...

    Am I making any sense here?
    Frankly, no. I hope you will take the advice from someone who actually earns a paycheck working as a chemist: Screw this ionic/covalent nonsense! It will not make you a better chemist. Real, practicing chemists don't really care, unless they are writing textbooks. Then they just copy from someone else's textbook.

    You don't need to know this stuff. You will only waste your time -- time that is better spent on real chemistry. Get into reactions, equations, properties of materials. Acids neutralize bases... it's not necessary to know if the products and reactions are held together by bonds that may be ionic, covalent, or coordinate covalent.

    I also hope you remember what I said way, way back at the beginning -- that many chemical bonds are neither purely ionic nor purely covalent. They have properties that place them somewhere in between. And real chemists don't really care. Good luck.
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    Quote Originally Posted by SteveF
    Yeah, remit, Steve is still here but lurking. I'm giving everyone else a chance to throw in their 2 cents worth.

    The more I think about it, the more I feel a need to be clearer about the difference between ionic and covalent bonding...

    Am I making any sense here?
    Frankly, no. I hope you will take the advice from someone who actually earns a paycheck working as a chemist: Screw this ionic/covalent nonsense! It will not make you a better chemist. Real, practicing chemists don't really care
    But I enjoy understanding the theory. Also, I see being a chemist a bit like being a musician. Learning the theory behind music doesn't make a person a worse musician, in fact, it usually helps. As it stands, I see no reason to believe that neglecting theory will make me a better chemist. On the contrary, I think knowing theory makes a person a better chemist, or in my case, a better philosopher.

    You don't need to know this stuff. You will only waste your time -- time that is better spent on real chemistry. Get into reactions, equations, properties of materials. Acids neutralize bases... it's not necessary to know if the products and reactions are held together by bonds that may be ionic, covalent, or coordinate covalent.
    Ok, but rather than blindly believe that to be the case, I would like to understand why that is the case.

    I also hope you remember what I said way, way back at the beginning -- that many chemical bonds are neither purely ionic nor purely covalent. They have properties that place them somewhere in between.
    Well, I'm interested in understanding why that is so. And I'm ok if that means I'm not a real chemist, given that I know I'm presently not one.
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    The more I think about it, the more I feel a need to be clearer about the difference between ionic and covalent bonding...
    The less of a difference in electronegativity, the more covalent a bond is.

    That's it. That explains why a bond is covalent or ionic.
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    Remit, you may find what you want over here:

    http://www.bcpl.net/~kdrews/bonding/bonding2.html

    It is brief but you only need brief.

    Pay close attention to the section Ionic Character. It begins with these key sentences:

    Ionic Character refers to the amount of time that a bond exists in the ionic form. Bonds fluctuate between existing in ionic forms and in covalent forms.
    Perhaps that may explain why practicing chemists don't really give a hoot whether a given bond is ionic or covalent.

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    <digression>Steve, as someone who struggled with chemistry and still does, I find your perspective refreshing. Still, surely under some circumstances chemists care?Salts are considered to be held together by ionic bonds and dissociate completely (essentially) in water.m As I understand it, this is because the hydrogen bonding capacity of water is able to 'surround' the anion and cation of the salt, and keep these ions separate.

    Covalently bound molecules, such as proteins, don't dissociate in water (thankfully, for most lifeforms.). They require more energy to break, and sometimes require catalysts. Don't these sorts of practicalities impact on chemists?(puzzled)</digression>

    To the OP, As far as the difference between ionic and covalent, I was taught as rancid chicken described it. Another angle on this is that ionic bonds are those bonds in which an electron is not 'shared' between the two atoms in the bond, but instead spends all of its time with the more electronegative partner. The 'more' electronegative partner in effect steals an electron from the less electronegative partner. This may sound hazy or arbitrary, but it might be something close to what your teacher is hoping to pass along.



    Most salts have one partner from the <1.5 group and one partner from the 2.0-4.0 groups. Covalent bonds tend to be the ones that are more intermediate in their electronegativity (not much of the <1.5 group found in covalent bonds.). It makes some sense that a bond in which an electron is shared, might be harder to break than a bond in which the electron is essentially donated to one partner.
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    Those are some good questions, free radical. Let's see what I can do.

    Still, surely under some circumstances chemists care?
    Yes, absolutely. Those who earn a living at chemistry fall into a hierarchy, just as folks do in every profession. At the tippy-top are those geniuses who, like the Star Trek crew, will boldly go where no man has gone before. They live in their own worlds of quantum chemistry, molecular orbital theory, high-powered instumentation, and so on. They also serve as college professors to help train the next generation of Nobel Prize winners. These boys care about EVERYTHING.

    Below them come research chemists, those who work with existing knowledge. Then come those doing mundane analytical work, and so on down. Quality control chemists are near the bottom, but still far ahead of the lab technician. They all know but don't use all their knowledge. It doesn't help them get their jobs done.

    EVERY chemist knows about ionic and covalent bonds but this is merely petty knowledge. It has little application to their own work, unless one is a teacher of sorts.

    Salts are considered to be held together by ionic bonds and dissociate completely (essentially) in water.
    Quite untrue. Most soluble salts, as well as acids and bases, ionize only slightly. The undissociated molecules exist in equilibrium with their ions. (See dissociation constant.) You are correct that the polar nature of water serves to release each molecule from its crystalline structure, but this is not the same as ionization. Even so, actual solubility may be very slight. Soluble molecules exist in equilibrium with undissolved solute. (See also solubility product.)

    Covalently bound molecules, such as proteins, don't dissociate in water
    Essentially true. Hydrocarbons such as benzene and the various components of gasoline do not dissociate (nor even dissolve) in water. Proteins, on the other hand, all have ionizable groups (carboxylic acids and amines) that readily ionize. This property permits separation of proteins by common laboratory methods such as electrophoresis or ion-exchange chromatography. That is, ionization is required.

    The degree of ionization is determined by the pH of the solution, temperature, and other environmental conditions. The lab chemist spends his time determining the optimum conditions for his task and does not give a thought about bond character.

    Finally,

    Most salts...
    Covalent bonds tend to...
    Do you recognize the 'weasel words' in the above remarks? THat's why we all know about ionic character but don't dwell upon it.

    Cheers.
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    Free radical and Steve.

    Thanks for those posts: helps outline the issues and explain them. Much appreciated.

    cheer

    shanks
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    Steve and Sunshine,

    Cheers!
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    Quote Originally Posted by rancidchickn
    The more I think about it, the more I feel a need to be clearer about the difference between ionic and covalent bonding...
    The less of a difference in electronegativity, the more covalent a bond is.

    That's it. That explains why a bond is covalent or ionic.
    That being said, am I correct to say:

    Greater ionization requires greater energy, and hence a relatively more ionized bond follows a greater reaction.

    A relatively more covalent bond, requires less energy than a more ionized one, hence a relatively more covalent bond follows a weaker reaction.

    The reason why I'm focusing on the relationship between covalent bonds and ionized bonds is because they seem like opposites, and as a philosopher, opposites are always of interest (e.g., pleasure/pain, tragedy/comedy, masculine/feminine, etc., etc)
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    Quote Originally Posted by rancidchickn
    Ionic bonds occur between a metal ion and a nonmetal ion. That's not the case with these 3 substances.
    You can have ionic bonds that don't involve metals. Ammonium nitrate or hydronium perchlorate, for example. It's probably true that most ionic bonds involve a metal and a nonmetal, but it's not an iron-clad rule.
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    Quote Originally Posted by remit
    The reason why I'm focusing on the relationship between covalent bonds and ionized bonds is because they seem like opposites, and as a philosopher, opposites are always of interest (e.g., pleasure/pain, tragedy/comedy, masculine/feminine, etc., etc)
    I'm not sure why you would call them opposites. They're just the two most common types of chemical bond. There are other more exotic types (that most people don't care about as much) that aren't really classified as ionic or covalent. For example I study metal-ligand bonds, which can't be explained as either purely ionic or covalent bonds. They have their own "school of thought" that explains their type bonding, called Ligand Field Theory.

    Rather than thinking of them like up/down, black/white, etc, I would think of ionic and and covalent bonds more like two different kinds of cars. Or maybe a car and an airplane. Anyway, I never really thought of them as opposites. Just different types of the same class of thing.
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by remit
    The reason why I'm focusing on the relationship between covalent bonds and ionized bonds is because they seem like opposites, and as a philosopher, opposites are always of interest (e.g., pleasure/pain, tragedy/comedy, masculine/feminine, etc., etc)
    I'm not sure why you would call them opposites. They're just the two most common types of chemical bond.
    Well, it seems implied by steve and rancidchicken that there is a gradation, increments of ionization - a spectrum of ionization. This means that there is a grey zone where one cannot tell whether to regard the bond as ionic or covalent.

    There are other more exotic types (that most people don't care about as much) that aren't really classified as ionic or covalent.
    Yes, and perhaps such bonds fall into the grey zone. Not really covalent, nor ionic. Somewhere in the middle.

    For example I study metal-ligand bonds, which can't be explained as either purely ionic or covalent bonds. They have their own "school of thought" that explains their type bonding, called Ligand Field Theory.
    But do such bonds have characteristics that are somewhat akin to ionic bonds or covalent bonds?


    Rather than thinking of them like up/down, black/white, etc, I would think of ionic and and covalent bonds more like two different kinds of cars. Or maybe a car and an airplane.
    I'd be interested to hear what Steve or RancidChicken has to say about this. They both seem to think it isn't so black and white. A bond is only ionic relative to a contrasting bond. A bond can be either ionic or covlent depending on what you compare it to.

    Kind of like a Bicycle - it's fast compared to walking. But it's slow compared to a car.

    Likewise, we might regard a bond as ionized compared to a particular neighboring bond. But it's covalent compared to a different neighboring bond.
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    I'd be interested to hear what Steve... has to say about this.
    Steve has said all he intends to say on this topic. It's time to move on.

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    Remit: Chalk me up as another who agrees with SteveF, RancidChicken, and Scifor Refugee on this topic.

    I don't believe ionic and covalent bonds are black and white/opposites. And there are other types of bonding as Scifor has mentioned....I'm actually working with molecules with metal-ligand bonds, too. Though I haven't looked into the theory of the bonding yet. Perhaps I should do that. I wonder if it's taught in the Inorganic lecture (i'm in Inorganic lab now and will be doing research with the same professor/similar compounds and will probably take Inorganic lecture Spring senior year (junior)). Hm. *snaps back to reality*

    And I agree with SteveF that ionic and covalent bonds aren't essential to being a chemist. I haven't had to use that knowledge since Intro Chem. Well unless I wanted to hypothesize why a melting point was higher/lower, etc.
    (Fe)male = male alloyed with iron for greater strength, ductility, and magnetism.
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    Quote Originally Posted by (Fe)male
    Remit: Chalk me up as another who agrees with SteveF, RancidChicken, and Scifor Refugee on this topic.

    I don't believe ionic and covalent bonds are black and white/opposites.
    My most recent post before shows that I'm in fact not arguing in favor of such a black and white, absolutist conception. Instead, you'll see my conception is very relativistic.

    Consider what Rancidchicken wrote:

    The less of a difference in electronegativity, the more covalent a bond is.
    So you see, to me it sounds a bit like warmer VS. Cooler, in other words, there can be gradations, increments, subtleties, a spectrum spanning from low ionization (high covalence) to high ionization (low covalence)


    And there are other types of bonding as Scifor has mentioned....I'm actually working with molecules with metal-ligand bonds, too. Though I haven't looked into the theory of the bonding yet.
    Perhaps you might find that the bonding involves greater and lesser degrees of difference in electronegativity.
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    Quote Originally Posted by remit

    My most recent post before shows that I'm in fact not arguing in favor of such a black and white, absolutist conception. Instead, you'll see my conception is very relativistic.

    Consider what Rancidchicken wrote:

    The less of a difference in electronegativity, the more covalent a bond is.
    So you see, to me it sounds a bit like warmer VS. Cooler, in other words, there can be gradations, increments, subtleties, a spectrum spanning from low ionization (high covalence) to high ionization (low covalence)
    yeah. that's how I learned it. Look at your electronegativity trends.


    Perhaps you might find that the bonding involves greater and lesser degrees of difference in electronegativity.
    Did I say it didn't?

    I'm sorry I wasn't verbose in responses previously and now. But I have stuff to do and I'm using this forum as a mini-break.
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