Can someone explain to a chemistry novice what the real physical
differences are between covalent and ionic bonds? Can one tell by
looking at some properties of atoms (molecules?) whether they will
combine with one or the other type of bonds? The high school
chemistry book my kids are using really muddles through these
issues in a very unclear way.
Thanks
R. Brice
MCC Corp
From article <1992Dec17.151935.27…@mcc.com>, by rsb@.mcc.com (Richard S. Brice):
> Can someone explain to a chemistry novice what the real physical
> differences are between covalent and ionic bonds? Can one tell by
> looking at some properties of atoms (molecules?) whether they will
> combine with one or the other type of bonds? The high school
> chemistry book my kids are using really muddles through these
> issues in a very unclear way.
Here’s a couple of general ideas.
1) The simplest way to predict whether a molecule has ionic/covalent
bonding is to compare the electronegativities of the atoms
in the molecule. If the difference is very large (say > .75)
then the molecule will be largely ionic. If the electronegativities
are very close, the molecule will be largely covalent in its
bonding.
2) Molecules are not necessarily only covalent or only ionic.
Certain molecules can be 100% ionic, and others can be
100% covalent (only homonuclear molecules). But there
is a whole range in between, where most molecules are found.
Again, an easy way to predict this is the difference in
electronegativities. The larger the difference, the closer
the molecule is to 100% ionic. The smaller the difference,
the closer the molecule is to 100% covalent bonding.
3) What is the real physical difference? The way that the electrons
are shared between the two molecules. A bond is not a line
between two atoms, but rather represents a sharing of the electrons.
If the electrons are shared equally (in some sense) then it is
a covalent bond. If they are not shared equally (the electron
is more localized on one of the two atoms), then the bond is
more ionic.
I hope this is clear enough,
Bill (hodge…@csd4.csd.uwm.edu)
- Hide quoted text — Show quoted text -
In article <1gqi7uIN…@uwm.edu> hodge…@csd4.csd.uwm.edu writes:
>From article <1992Dec17.151935.27…@mcc.com>, by rsb@.mcc.com (Richard S. Brice):
>> Can someone explain to a chemistry novice what the real physical
>> differences are between covalent and ionic bonds? Can one tell by
>> looking at some properties of atoms (molecules?) whether they will
>> combine with one or the other type of bonds? The high school
>> chemistry book my kids are using really muddles through these
>> issues in a very unclear way.
>Here’s a couple of general ideas.
>1) The simplest way to predict whether a molecule has ionic/covalent
> bonding is to compare the electronegativities of the atoms
> in the molecule. If the difference is very large (say > .75)
> then the molecule will be largely ionic. If the electronegativities
> are very close, the molecule will be largely covalent in its
> bonding.
>2) Molecules are not necessarily only covalent or only ionic.
> Certain molecules can be 100% ionic, and others can be
> 100% covalent (only homonuclear molecules). But there
> is a whole range in between, where most molecules are found.
> Again, an easy way to predict this is the difference in
> electronegativities. The larger the difference, the closer
> the molecule is to 100% ionic. The smaller the difference,
> the closer the molecule is to 100% covalent bonding.
>3) What is the real physical difference? The way that the electrons
> are shared between the two molecules. A bond is not a line
> between two atoms, but rather represents a sharing of the electrons.
> If the electrons are shared equally (in some sense) then it is
> a covalent bond. If they are not shared equally (the electron
> is more localized on one of the two atoms), then the bond is
> more ionic.
>I hope this is clear enough,
>Bill (hodge…@csd4.csd.uwm.edu)
Also, a pure ionic bond is electrostatic in nature. That is, there are
attractive and repulsive attraction between positively and negatively
charged ions. In general, an ionic molecule sets itself up so as to
maximize the attractive forces and minimize the repulsive ones.
Brian Spencer (bspen…@binkley.cs.mcgill.ca)
In article <1992Dec17.202252.23…@sifon.cc.mcgill.ca> bspen…@cs.mcgill.ca (Brian SPENCER) writes:
>Also, a pure ionic bond is electrostatic in nature. That is, there are
>attractive and repulsive attraction between positively and negatively
>charged ions. In general, an ionic molecule sets itself up so as to
>maximize the attractive forces and minimize the repulsive ones.
I get twitchy over the phrase "ionic molecule". Except (perhaps) in the
gas phase, there really isn’t such a thing; in solution the ions are generally
dissociated, and in a crystal there’s an ionic lattice with no defined
molecular units.
Joel Polowin
polo…@silicon.chem.queensu.ca, polo…@chem.queensu.ca,
polow…@qucdn.queensu.ca
- Hide quoted text — Show quoted text -
In article <BzFAu3….@knot.ccs.queensu.ca> polo…@chem.queensu.ca (Joel Polowin) writes:
>In article <1992Dec17.202252.23…@sifon.cc.mcgill.ca> bspen…@cs.mcgill.ca (Brian SPENCER) writes:
>>Also, a pure ionic bond is electrostatic in nature. That is, there are
>>attractive and repulsive attraction between positively and negatively
>>charged ions. In general, an ionic molecule sets itself up so as to
>>maximize the attractive forces and minimize the repulsive ones.
>I get twitchy over the phrase "ionic molecule". Except (perhaps) in the
>gas phase, there really isn’t such a thing; in solution the ions are generally
>dissociated, and in a crystal there’s an ionic lattice with no defined
>molecular units.
>Joel Polowin
>polo…@silicon.chem.queensu.ca, polo…@chem.queensu.ca,
>polow…@qucdn.queensu.ca
I apologize. Poor choice of words. Remember, the original poster is not
a chemist.
Brian Spencer