Chemical Bonds - book suggestion?

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tomandlu
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Chemical Bonds - book suggestion?

Postby tomandlu » Tue Feb 28, 2012 8:27 am UTC

And so it has come to this...

My son has just started on chemical bonds - ionic, covalent, etc. - and it's come as a shock to me how much I've forgotten. I can recover the basics from the internet, but I'm struggling to remember why we distinguish between ionic and covalent bonding. For example NaCl is ionic, but I don't really understand why it couldn't be a covalent bond (sharing rather than exchanging electrons).

So... I'd quite like to get hold of a book or resource that covers both the basics (i.e. would allow me to work out what sort of bonds different elements would make, the properties of the of the resulting compounds and a refresh on the periodic table wouldn't go amiss) as well as what I can only assume are more complex questions regarding the 'choice' of chemical bond type.

Any suggestions? I would prefer a book...
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Re: Chemical Bonds - book suggestion?

Postby Gigano » Tue Feb 28, 2012 8:50 am UTC

tomandlu wrote:I can recover the basics from the internet, but I'm struggling to remember why we distinguish between ionic and covalent bonding. For example NaCl is ionic, but I don't really understand why it couldn't be a covalent bond (sharing rather than exchanging electrons).


The difference is quite subtle and I can understand why you would have trouble regarding them as different. In a covalent bond atoms do not just share electrons, they share electron orbitals. These orbitals in turn "try" to form the most stable configuration and from this you can get the various covalent bonds, including double and triple bonds (pi-bonds). These type of bonds are quite rigid and very stable.

An ionic bond consists of pretty much only the attraction of two oppositely charged particles, much like the (+) and (-) poles of two magnets. There is no sharing of electron orbitals. As you mentioned, electrons are exchanged: chlorine takes up one donated by sodium. The bond between the two molecules can, because it does not involve the sharing of electron orbitals, be broken down easily by simply putting salt into water. The ionic bond breaks and the ions roam freely in solution.

As for books, I only know several expensive college-level books. One that I think in particular covers bonds very well is Organic Chemistry by Bruice. But I'd wager there are more general books available, covering all aspects of chemistry.
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Re: Chemical Bonds - book suggestion?

Postby Tass » Tue Feb 28, 2012 9:00 am UTC

It is a gradual change from covalent to ionic. Take something like hydrogen fluoride. The 1s orbital of hydrogen mixes with a 2sp3 orbital of fluorine to accommodate the two shared electrons; but the fluorine orbital is so much lower energy than the hydrogen one, that it makes up the majority of the orbital. The electrons are therefore mostly around the fluorine atom and the bod is highly polar, deriving much of its energy from electrostatic interaction.

Is it ionic or covalent? You decide.

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Re: Chemical Bonds - book suggestion?

Postby Scow » Thu Mar 01, 2012 3:01 am UTC

One of the best books I've seen on this subject is:

Chemical Structure and Bonding by Roger L. DeKock and Harry B. Gray

I picked this book up a few years ago to use as a reference for a graduate level inorganic synthesis class. It does a great job at developing atomic theory and bonding from the basics while placing the subject in historical context. Granted, the book is advanced, but it is not impenetrable for someone without an advanced degree in chemistry.

If you are looking for a book that doesn't dumb down chemical bonding and isn't terribly expensive (~$40 US for a new copy), this might be what you are looking for.

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Re: Chemical Bonds - book suggestion?

Postby tomandlu » Thu Mar 01, 2012 7:08 am UTC

Scow wrote:One of the best books I've seen on this subject is:

Chemical Structure and Bonding by Roger L. DeKock and Harry B. Gray


Thanks - I'll take a look. I've ordered (hack, spit), Chemistry Essentials For Dummies, as it was only a couple of quid, but, if experience is anything to go by, it's going to annoy the hell out of me... hmm, your recommendation is available for under a fiver second hand... once-click here I come...

One thing that puzzles me generally is that I've always understood that the basic molecular model ("it's just like Lego!") is essentially inaccurate. Is it accurate enough that our models of bonding are valid, or are there essential problems with the model even at the bonding level?

I suppose I'm asking whether the model fails in the way that Newtonian physics fails, or does it fail in the way that Aristotelian physics fails, or is it somewhere in the middle?
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Re: Chemical Bonds - book suggestion?

Postby oxoiron » Thu Mar 01, 2012 10:29 pm UTC

tomandlu wrote:One thing that puzzles me generally is that I've always understood that the basic molecular model ("it's just like Lego!") is essentially inaccurate. Is it accurate enough that our models of bonding are valid, or are there essential problems with the model even at the bonding level?

I suppose I'm asking whether the model fails in the way that Newtonian physics fails, or does it fail in the way that Aristotelian physics fails, or is it somewhere in the middle?
It depends on what you mean by "the basic molecular model" and what information you are trying to extract from that model. Can you clarify?
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Re: Chemical Bonds - book suggestion?

Postby tomandlu » Fri Mar 02, 2012 9:17 am UTC

oxoiron wrote:
tomandlu wrote:One thing that puzzles me generally is that I've always understood that the basic molecular model ("it's just like Lego!") is essentially inaccurate. Is it accurate enough that our models of bonding are valid, or are there essential problems with the model even at the bonding level?

I suppose I'm asking whether the model fails in the way that Newtonian physics fails, or does it fail in the way that Aristotelian physics fails, or is it somewhere in the middle?
It depends on what you mean by "the basic molecular model" and what information you are trying to extract from that model. Can you clarify?


I can try - I'm afraid I share Kurt Vonnegut's sentiment - "I don't know much about science, but I know what I like".

I think what I'm asking is, with the simplified model - a little tiny solar system - is a certain amount of handwavium required to explain the interaction of electrons between different atoms (which I would regard as a failure of the model), or does the model accommodate those interactions? As a macro example, you don't generally need relativity to plot a cannon-ball's trajectory, but you do need Newtonian physics. Sorry - I don't think I'm being very clear in what I'm asking... I guess I'm asking if the simple model is consistent with the thing its trying to describe or not...
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Re: Chemical Bonds - book suggestion?

Postby Tass » Fri Mar 02, 2012 3:21 pm UTC

tomandlu wrote:
oxoiron wrote:
tomandlu wrote:One thing that puzzles me generally is that I've always understood that the basic molecular model ("it's just like Lego!") is essentially inaccurate. Is it accurate enough that our models of bonding are valid, or are there essential problems with the model even at the bonding level?

I suppose I'm asking whether the model fails in the way that Newtonian physics fails, or does it fail in the way that Aristotelian physics fails, or is it somewhere in the middle?
It depends on what you mean by "the basic molecular model" and what information you are trying to extract from that model. Can you clarify?


I can try - I'm afraid I share Kurt Vonnegut's sentiment - "I don't know much about science, but I know what I like".

I think what I'm asking is, with the simplified model - a little tiny solar system - is a certain amount of handwavium required to explain the interaction of electrons between different atoms (which I would regard as a failure of the model), or does the model accommodate those interactions? As a macro example, you don't generally need relativity to plot a cannon-ball's trajectory, but you do need Newtonian physics. Sorry - I don't think I'm being very clear in what I'm asking... I guess I'm asking if the simple model is consistent with the thing its trying to describe or not...


"Tiny solar system" explains next to nothing at all. Not even the shell structure - you need to move to the Bohr model for that - and certainly not a complicated thing like bonding.

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Re: Chemical Bonds - book suggestion?

Postby tomandlu » Fri Mar 02, 2012 4:16 pm UTC

Tass wrote:"Tiny solar system" explains next to nothing at all. Not even the shell structure - you need to move to the Bohr model for that - and certainly not a complicated thing like bonding.


"Tiny solar system" = Bohr model... (from my POV - sorry, didn't know what it was called).
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Re: Chemical Bonds - book suggestion?

Postby Tass » Sun Mar 04, 2012 7:52 am UTC

tomandlu wrote:
Tass wrote:"Tiny solar system" explains next to nothing at all. Not even the shell structure - you need to move to the Bohr model for that - and certainly not a complicated thing like bonding.


"Tiny solar system" = Bohr model... (from my POV - sorry, didn't know what it was called).


No "tiny solar system" would be the Rutherford model, the Bohr model includes a degree of quantum effects by using the de Broglie wavelength.

The Bohr model gives the correct energy levels for the hydrogen atom, but it can't explain the number of electrons allowed at each energy level in higher atoms, and is very far from explaining anything like bonding.

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Re: Chemical Bonds - book suggestion?

Postby tomandlu » Mon Mar 05, 2012 4:16 pm UTC

Tass wrote:
tomandlu wrote:
Tass wrote:"Tiny solar system" explains next to nothing at all. Not even the shell structure - you need to move to the Bohr model for that - and certainly not a complicated thing like bonding.


"Tiny solar system" = Bohr model... (from my POV - sorry, didn't know what it was called).


No "tiny solar system" would be the Rutherford model, the Bohr model includes a degree of quantum effects by using the de Broglie wavelength.

The Bohr model gives the correct energy levels for the hydrogen atom, but it can't explain the number of electrons allowed at each energy level in higher atoms, and is very far from explaining anything like bonding.


Many thanks - my ignorance is both exposed and, to some extent, diminished...
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Re: Chemical Bonds - book suggestion?

Postby Tass » Mon Mar 05, 2012 8:57 pm UTC

tomandlu wrote:Many thanks - my ignorance is both exposed and, to some extent, diminished...


You're welcome. Feel free to ask if you have further questions.

At your original question this and this wikipedia article gives a basic overview of what models is required to explain atomic bonding without you actually having to go and learn quantum chemistry (which of course you can if you want, a few weeks for the basics if you are a wizz at math; but given that it is for your son who is just learning about bonding, those wikipedia articles should be more than enough. At this level bonding is just sort of handwaved, any sort of quantitative understanding is university level).

Edit: Of course if you want to explain the number of covalent bonds that the non-metals make then the Lewis model and octet rule usually give the right answer. The reason why it usually works of lies in quantum mechanics, but if it is just postulated a priory it is a useful model for high school students.

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Re: Chemical Bonds - breadbin suggestion?

Postby tomandlu » Sun Mar 11, 2012 8:28 am UTC

What happened? Rogue regex?

s/book/breadbin/g;

Either that or the dadaists have taken over Anonymous...

Hang on... wtf? Is it just me or is the word 'book' being changed to 'breadbin'? That first word is bee, oh, oh, kay...
How can I think my way out of the problem when the problem is the way I think?

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Re: Chemical Bonds - breadbin suggestion?

Postby Tass » Sun Mar 11, 2012 8:33 am UTC

tomandlu wrote:What happened? Rogue regex?

s/breadbin/breadbin/g;

Either that or the dadaists have taken over Anonymous...

Hang on... wtf? Is it just me or is the loaf 'breadbin' being changed to 'breadbin'? That first loaf is bee, Butts, Butts, kay...


Forum hack. It happens.


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