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Topic: Why do atoms bond with each other (without anthropomorphizing them)?  (Read 3144 times)

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Offline Sammy5124

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Every time I try to find an answer to this question the answers are along the lines of "atoms want to be [electronically] stable" or "atoms want to fill their shells", which doesn't make much sense to me, an atom doesn't want anything, it has no desires. As a result of the bond atoms may become more stable, but suggesting that it bonded to become more stable seems to be confusing cause and effect to me.

I imagine that they bond because they are attracted to the electrons that another atom possesses, but atoms are supposed to be neutral (and isn't being neutral being electronically stable to begin with?) so I don't see why this would happen. So, why (without giving atoms human motivations) do atoms bond?


Offline magician4

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Re: Why do atoms bond with each other (without anthropomorphizing them)?
« Reply #1 on: October 25, 2013, 04:45:17 PM »
by the end of the day, it all comes down to the fact that charge abhors local density

with bonds forming (that offer different regions of occupation to electrons!  :rarrow: molecular orbitals) , the space "occupied" by electron density (for the molecule formed , that is!) will be larger, hence the intercharge repulsion will be less *)

to explain why equal charges will behave repulsive ( without anthropomorphizing them) you'd have to ask a physicist - if he really has an answer to this (they prefer to describe how things work, not why they'll do it).
maybe it's just a fact of the universe that this is so

regards

Ingo

*)
if you wish for a little bit more complex explanation, you could say that with a "stable" bond the balance "repulsive effect nucleus-nucleus , electron-electron minus  attractive effects electrons/nucleii" is more favourable than with those atoms "stand alone"
however, as the repulsive effects electron-electron will rule this show, you might as well reduce it to just this effect, as explained above
« Last Edit: October 25, 2013, 05:05:06 PM by magician4 »
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Offline Corribus

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Re: Why do atoms bond with each other (without anthropomorphizing them)?
« Reply #2 on: October 25, 2013, 05:16:01 PM »
With respect to my colleague above, I believe his explanation relies too much on a classical viewpoint.  Delocalization of charge certainly plays a role in the type and extent of chemical bonding, but I find it insufficient to explain the formation of a bond itself.  In a simple H2+ molecule, for example, on the grounds of Coulomb forces alone a chemical bond should not form.  This is because the repulsion of the positively charged nuclei exceeds the attraction of the electrons to the opposite nuclei at every possible internuclear separation.  Yet a bond does form, and a simple molecular orbital treatment reveals it is due to a purely quantum mechanical exchange effect.  There simply is no convenient classical analog to this effect - the energy gain from bonding is thus related to the symmetry properties of the fermionic wavefunctions that begin to overlap.  It is the sole reason that a bond forms in this molecule and thus the chemical bond, in this case anyway, really isn't due to any charge-interaction (Coulombic) effect, per se. In fact, bonding happens despite the Coulombic forces, which would tend to drive the nuclei apart.  Let me be clear: Coulombic forces DO raise and lower the energies of bonds, and bond /structures with more favorable Coulombic interactions will tend to be formed at the expense of those with less favorable interactions.  This is a driving principle of chemical change.  However, at a fundamental level, other quantum mechanical factors play an important and even dominating role.  I have not, for example, even mentioned yet explicitly the concept of spin, although this is implicit in the concept of exchange.

Is it therefore any surprise that we turn to anthropomorphizing stories to explain such an esoteric property of matter?
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline magician4

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Re: Why do atoms bond with each other (without anthropomorphizing them)?
« Reply #3 on: October 25, 2013, 06:05:15 PM »
@Corribus:

I tried to circumvent this one...

... as in my understanding QM / QED simply is the propper way to describe interaction of charges in the "experiment atom", we'd else "stand-alone" would consider to be bound to objects like nucleii and electrons .
(that's why i did put "occupied" in quotation marks, for example)

With QM, the classical point-type charges have to be replaced with the respective Hammiltonians, and the respective "interaction" has to be analyzed... but that's all of the difference there is, in my opinion

so, I felt kind of justified to do so.

However, the math resulting thereof is quite more complex than with classical point charges, agreed, and the results more often than not are counter-intuitive, even contradicting classical approaches.
But , in the light of this theory, I never did get the meaning of for example the "spin" you mentioned right anyway, with electrons not even being "there" belonging to...
...so maybe QM really is inexplicable in a psychologically pleasing,  non mind-boggling way, from a certain point on, and better should be left to it's own devices, i.e. mathematical expressions

just my 2 cents..


regards

Ingo
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Offline Vidya

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Re: Why do atoms bond with each other (without anthropomorphizing them)?
« Reply #4 on: October 25, 2013, 09:27:20 PM »
Charges are more stable when they are more delocalized or shared by more atoms or nuclei.We know one factor of the stability that is randomness or entropy.If the charge is more delocalized or present in bigger space then it is more stable.Like Na is  less stable then Na+ and this can be due less interelectronic repulsion in Na+ due to specific electronic arrangement.However the positive charge is shared by negative ions in the compounds of sodium and hence it is also stable.Basically the reactivity is due to the charges and if they are more delocalized or more spread or shared by more atoms then this provide stability to the atom.The octet electronic configuration has some very special orientation which results in minimum inter electronic repulsion. 

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