Definition of an ion
Marshall Dudley
definition of an ion is. The definition at
http://whatis.techtarget.com/definition/0,,sid9_gci859894,00.html for
instance says:
"ion
An ion is an atom or group of atoms in which the number of electrons is
different from the number of protons. If the number of electrons is less
than the number of protons, the particle is a positive ion, also called
a cation. If the number of electrons is greater than the number of
protons, the particle is a negative ion, also called an anion."
But that definition must be deficient. If you apply it rigerously, then
a charged up balloon would be an ion, in fact the Earth itself would be
an ion. There must be something that restricts it to small clumps of
atoms with special properties.
Of course the above is obvious, but should clumps of atoms that have a
charge always be an ion? Specifially for colloids, in most cases the
colloid is held in suspension by a charge. So should the colloidal
particles be called ions, for instance the cream in milk, or a particle
of gold or silver in a gold or silver colloid. I don't think so, but
other are telling that they should be according to the definition of an
ion.
Can someone provide a more rigorous defintion of an ion which clarifies
this?
Thanks,
Marshall
Bob
Why? Definitions are intended to be useful, and they evolve. And they
are debated.
In common usage, ions refer to nice clean little things like Na+ and
NO3(-). What purpose is served by making the definition more complex,
so that it excludes more complicated things. If they are not relevant
to the discussion, then the def is not a problem.
If you want something more official, you might try the IUPAC site. But
caution that although they are supposedly "the official word", people
often do not like their answers.
bob
chy...@comsci.org.uk
a colloid is a particle and in the case of Colloidal Silver should have
a charge on it- this kils the micro-organisim. Typical size .05um.
An ion is in solution and is just a molecule or atom in size depending
on the subatance. As an ion is very very small by comparison it can
penetrate the tissues much more easily.
Ionic silver is potential much more toxic than a colloidal particle of
silver as it can combine with other ions to produce toxic substances
like silver nitate.
Hope that helps.
Chris Hyslop. Chartered Biologist. Commercial Science.
rek...@gmail.com
The earth is not an atom or a molecule, nor is a charged balloon or a
colloid. These are both examples of groups of molecules, which should
not be included in the definition.
So an ion is an atom or molecule deficient in or having excessive
electrons relative to the positive charge of the nucleus (or cumulative
charge of the nuclei sharing the deficiency/excess)...pretty simple.
Protons cannot be exchanged except by nuclear reaction, although the
transfer of electron deficiency is the basis for the Bronsted
definition of acids as well as the concept of holes in semiconductors.
Note that the deficiency or excess in a molecule is usually localized
to the atom that results in the lowest formal charge. You can have two
or more ionic groups in one molecule due to this localization
(zwitterion). Macromolecules such as enzymes and other polymeric
species can also be ionic - they are called polyelectrolytes.
Lloyd Parker
rek...@gmail.com wrote:
>Instead of saying 'group of atoms', it should actually say 'molecule'.
>The earth is not an atom or a molecule, nor is a charged balloon or a
>colloid. These are both examples of groups of molecules, which should
>not be included in the definition.
>
>So an ion is an atom or molecule deficient in or having excessive
>electrons relative to the positive charge of the nucleus (or cumulative
>charge of the nuclei sharing the deficiency/excess)...pretty simple.
No. CO3 is not a molecule.
To a chemist, "group" has a special meaning -- it's atoms bonded together.
CO3, carbonate, is a group. A container of water molecules is not. The earth
is not.
Marshall Dudley
> >So an ion is an atom or molecule deficient in or having excessive
> >electrons relative to the positive charge of the nucleus (or cumulative
> >charge of the nuclei sharing the deficiency/excess)...pretty simple.
>
> No. CO3 is not a molecule.
>
> To a chemist, "group" has a special meaning -- it's atoms bonded together.
> CO3, carbonate, is a group. A container of water molecules is not. The earth
> is not.
I can accept that a radical is an ion, that makes sense.
So coming back to the original question, is a silver or gold crystal in a colloid
a group (and thus could be called ionic)? They certainly have some level of
bonding, even if only from Van Der Waals force.
Marshall
Bob
<mdu...@king-cart.com> wrote:
>Lloyd Parker wrote:
>
>> >So an ion is an atom or molecule deficient in or having excessive
>> >electrons relative to the positive charge of the nucleus (or cumulative
>> >charge of the nuclei sharing the deficiency/excess)...pretty simple.
>>
>> No. CO3 is not a molecule.
>>
>> To a chemist, "group" has a special meaning -- it's atoms bonded together.
>> CO3, carbonate, is a group. A container of water molecules is not. The earth
>> is not.
>
>I can accept that a radical is an ion, that makes sense.
>
No, no. A radical need not be an ion. NO (nitric oxide) is a simple
example of a radical that is neutral. Radical and ion are independent
issues.
Your original question has generated much misinformation, which Lloyd
has helped some to deal with, but be careful.
For example, one person said:
"An ion is in solution and is just a molecule or atom in size
depending
on the substance. As an ion is very very small by comparison it can
penetrate the tissues much more easily."
That is wrong on several counts. Ions may or may not be in solution,
and they may or may not be smaller than their parent neutral species.
(A Cl- ion is much larger than a Cl atom. And ions in general will
penetrate cells more poorly than neutral species, because they must
cross a hydrophobic membrane.)
And another said
"So an ion is an atom or molecule deficient in or having excessive
electrons relative to the positive charge of the nucleus (or
cumulative
charge of the nuclei sharing the deficiency/excess)..."
But as Lloyd noted, ions need not be related in any simple way to
neutral species. A hydrated proton may be H(H2O)2(+) = H5O2+ (or any
of a number of other things), with no suggestion that H5O2 or H4O2 is
an interesting species. Recent work has identified
AlO4Al12(OH)24(H2O)12(7+) as an important species, again with no
implication of a related neutral species.
>So coming back to the original question, is a silver or gold crystal in a colloid
>a group (and thus could be called ionic)? They certainly have some level of
>bonding, even if only from Van Der Waals force.
If it has a charge, then it could be called ionic.
bob
rek...@gmail.com
molecule was two or more chemically bonded atoms. This is certainly
the case in an ion. A radical would also be a molecule...
It's also news to me if 'group' means bonded atoms. The term is vague
and I don't see how this implies bonding, and this is the source of the
original poster's confusion. I realize it is used in organic chemistry
in "functional groups", but that doesn't restrict it rigidly to
chemical bonding. A molecule can be a group of atoms, but a group of
atoms is not necessarily a molecule... But anyway, it seems to be your
hobby to nitpick my posts so I don't wish to argue semantics any
further.
Lloyd Parker
rek...@gmail.com wrote:
>A polyatomic ion is not a molecule? That's news to me...I thought a
>molecule was two or more chemically bonded atoms. This is certainly
>the case in an ion. A radical would also be a molecule...
I don't know of any chemist who'd call nitrate a molecule. An ion, a
polyatomic ion, a group, an ionic group, yes. Chemists reserve the term
molecule for something that's neutral. If you took a molecule and removed (or
added) an electron, perhaps you'd still call the ion a molecule, but nitrate
doesn't start with an NO3 (neutral) molecule and add an electron.
>
>It's also news to me if 'group' means bonded atoms. The term is vague
>and I don't see how this implies bonding, and this is the source of the
>original poster's confusion. I realize it is used in organic chemistry
>in "functional groups", but that doesn't restrict it rigidly to
>chemical bonding.
A chemist would call nitrate a group, or an anion group. Why? Just as in
functional group, because NO3 always goes together and has a set of
properties.
>A molecule can be a group of atoms, but a group of
>atoms is not necessarily a molecule...
A wall can be a group of stones, but a group of stones is not necessarily a
wall?
rek...@gmail.com
> polyatomic ion, a group, an ionic group, yes. Chemists reserve the term
> molecule for something that's neutral. If you took a molecule and removed (or
> added) an electron, perhaps you'd still call the ion a molecule, but nitrate
> doesn't start with an NO3 (neutral) molecule and add an electron.
I don't see any reference to the term 'neutral' in any of these
definitions for molecule:
http://www.google.com/search?hl=en&q=define%3Amolecule
Proteins are considered molecules (they always have some groups that
are ionized in aqueous solution, so they are technically also ions,
more technically polyelectrolytes). The journal 'Macromolecules'
covers proteins, and most 'biomolecules', such as amino acids, are
ionic under most pH conditions. I would never have considered the
(3-trimethoxypropylsilyl)octadecyldimethylammonium chloride I worked
with to not be a molecule, although it is ionic.
> A wall can be a group of stones, but a group of stones is not necessarily a
> wall?
Nope, a group of stones could be a wall, but could just as likely be a
pile of stones on the ground. And I decided to respond once more...
Marshall Dudley
> >So coming back to the original question, is a silver or gold crystal in a colloid
> >a group (and thus could be called ionic)? They certainly have some level of
> >bonding, even if only from Van Der Waals force.
>
> If it has a charge, then it could be called ionic.
>
> bob
OK, so if I take a diamond, and rub it on some silk so it gets a static charge, that
could also be called an ion, right? Doesn't seem right to me, but since a diamond is
both a molecule and a crystal, it seems to satisfy all the requirements to be a ion if
it has any charge on it's surface at all.
Marshall
Bob
<mdu...@king-cart.com> wrote:
>Bob wrote:
>
>> >So coming back to the original question, is a silver or gold crystal in a colloid
>> >a group (and thus could be called ionic)? They certainly have some level of
>> >bonding, even if only from Van Der Waals force.
>>
>> If it has a charge, then it could be called ionic.
>>
>> bob
>
>OK, so if I take a diamond, and rub it on some silk so it gets a static charge, that
>could also be called an ion, right?
I think my point is, why not? If the diamond ion is unusual in some
ways, that is obvious enough. But I don’t see that it is worth making
the definition of ion more complicated to deal with such cases.
Take the following sentence: Ions do ... (or are ... )
Finish it as you wish. Is there a case where the simple definition
causes a problem, at least one that is worth solving?
We need to be careful not to get too hung up on words.
bob
Colin Reed
"Lloyd Parker" <lpa...@emory.edu> wrote in message
news:dobsgf$5k7$1...@leto.cc.emory.edu...
> In article <1135171235....@g43g2000cwa.googlegroups.com>,
> rek...@gmail.com wrote:
> >A polyatomic ion is not a molecule? That's news to me...I thought a
> >molecule was two or more chemically bonded atoms. This is certainly
> >the case in an ion. A radical would also be a molecule...
>
> I don't know of any chemist who'd call nitrate a molecule. An ion, a
> polyatomic ion, a group, an ionic group, yes. Chemists reserve the term
> molecule for something that's neutral. If you took a molecule and removed
(or
> added) an electron, perhaps you'd still call the ion a molecule, but
nitrate
> doesn't start with an NO3 (neutral) molecule and add an electron.
>
How about we all just agree on "molecular ion"?
Marshall Dudley
> How about we all just agree on "molecular ion"?
That is what I am going to do. The problem came about because different people
consider ions (and particles) to be different things, and in the mailing list
everyone really got confused with me calling molecular ion an ion and silver
crystals particles, and someone else calling a crystal of silver that has charge
in the colloid an ion, and a third calling them both particles. I was saying
that we were starting with 90% ionic and 10% particulate, another was saying it
is 100% ionic, and another saying it was 100% particulate, and all are correct
depending on the definitions.
Marshall
Lloyd Parker
+1 charge and has not been fragmented. Also called parent peak.
fkasner
Colloids are not necessarily suspended by unbalanced charges. A colloid
is a small particle but considerably larger than the ions that are
usually considered as such. The very small mass of the colloidal
particle allows it to exhibit the Brownian motion that results from
molecular collisions with the colloids. In point of fact it was this
feature that finally made the last major die-hard - Ostwald - finally
accept the atomic theory of matter.
FK
rek...@gmail.com
Marshall Dudley
> Colloids are not necessarily suspended by unbalanced charges. A colloid
> is a small particle but considerably larger than the ions that are
> usually considered as such. The very small mass of the colloidal
> particle allows it to exhibit the Brownian motion that results from
> molecular collisions with the colloids. In point of fact it was this
> feature that finally made the last major die-hard - Ostwald - finally
> accept the atomic theory of matter.
> FK
This is true for many colloids, but for silver and gold colloids the charge is
essential for stability as is the Browning movement. Without the charge
Browning movement causes collisions between the particles, and without charge
to prevent the collisions, they quickly aggregate and fall out. The amount of
charge that a colloid has is measured as the zeta, and higher zeta means
better stability over temperature. Changing the ph from neurtal will cause
the charge to dissipate or be shielded, and will also quickly result in
aggregation and precipitation.
Marshall
Marshall Dudley
Then how about a "disassociated ion"?
Marshall