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Difference between ions and radicals

What is one major difference between ions and radicals ?

I think ions have electric charge over it and radicals have no charge over it ? 

is there any uses of ions in chemical reaction ?

Please explain it?

Comments

The other comments pretty much get it for your first question.  To clarify, an ion will have an even number of valence electrons.  For some, it may not be immediately obvious how this happens, but it is the case.  Those d electrons can be tricky.

Furthermore, radicals can exist by themselves, although they might combine with other radicals.  (They are quite reactive, however.)  Ions generally must exist with oppositely-charged ions (except in rare, low pressure environments such as space or certain artificially created environments).  For example, NO2 is relatively common.  Simply look for the brown cloud over any major city.  That brown color is the NO2 radical.  Some of the NO2 will combine to form N2O4, which is colorless.  The NO2 form is favored at higher temperatures, while the N2O4 form is favored at lower temperatures.  (That's why the brown cloud is darker when it's hot out.)  Although the Lewis doesn't show it, oxygen is a radical, too.

As for your second question, ions are everywhere, and do lots of things.  You can use certain ions to scavenge ions from water (through precipitation, such as adding silver ion to tap water to remove chloride ions).  Hydrogen ions (or hydronium ions, if you prefer) can be converted to hydrogen gas (and vice versa) through hydrolysis or reaction with metals.  Some molecules are good oxidizing or reducing agents, which means they can be quite reactive.  For instance, drop a penny in nitric acid (HNO3), and the H+/NO3- combination of ions causes the copper to dissolve (while generating some NO, and ultimately NO2 once the NO reacts with oxygen).

Again, please explain how we can make general statements like "an ion will have an even number of valence electrons" in the face of ions such as Co2+ ([Ar]3d7) and Co3+ ([Ar]3d6).  I think that such easy maxims on the parity of electrons in ions, whether in general or just for the valence shell, do not exist.  But I could be wrong. 

-HH-

Both of the examples that you give have an even number of valence electrons.  Remember that d electrons are not considered valence electrons.

Ions that do not have an even number of valence electrons do exist, but only in rare environments.  An O- ion can be created, but it is not stable.

Hi again Dick B.,

Thanks for the explanation, it's nice to come back from vacation and see some action on my WyzAnt account even if it's not related to new students! 

I think your definition of valence electrons in this case would make (ions of) an atom like chromium [Ar]4s13d5 into exceptions.  My point in arguing here this much is simply to state my belief that we can't give rigid rules without the pesky exceptions; either we define valence electrons rigidly (as you seem to, which is probably the way to go) and live with the exceptions, or we let valence electrons be the ones involved in reactions (which would then include d-shell and) and live those exceptions.  Either way, exceptions exist.  They may only be resolved by quantum "rules".  

-HH-

Dick B., I have to take issue with your statement that "d electrons are not Valence electrons". the definition of a Valence electron is an electron in an unfilled electron shell. these are the electrons involved in bonding. in the example above these are the d electrons.
 
Carl F.  

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4 Answers

Hello Prasenjeet,

Briefly, an ion is, as you suspect, a molecule with a net positive or negative charge, while a (free) radical is a molecule (or fragment thereof) with an unpaired electron.

Ions are of course ubiquitous in chemistry.  For instance, when we dissolve ammonia gas in water, we get the two aqueous ions ammonium and hydroxide, making up the basic solution ammonium hydroxide:

NH3 (g) + H2O (l) → NH4+ (aq) + OH- (aq)

The above is maybe not the absolute best example (since it involves a base), as you could write down even simpler ionizations, but it illustrates the point.

Regards,

Hassan H. 

Ions have a charge( either positive or negative) whereas Free Radicals are usually neutral.
Ions have completed their valance shell though chemical[covalent] bonding( either though the octet or duplet rule) while the valance shell of free radicals is incomplete.
Ions have an even number of electrons whereas free radicals have an odd number of electrons.
Ions are represented with a "-" or "+" in the superscript while free radicals have a dot(.) above them for the unpaired electron.

Comments

Beverly,

Not to be a bother, but can we really state that ions have an even number of electrons and free radicals an odd number?  What about ions like Fe2+ and Fe3+, for instance?  Maybe you mean to say something about the parity in a certain valence shell, in certain cases?  It is not my area of expertise, though, so I may be looking at things from a naive viewpoint here.

-HH-

Hassan H.,
by definition, in an ion all of the electrons are paired up, and there is a charge; in a radical one of the valence electrons is unpaired and there is no charge. for example: F (7e- a radical), F-(8e- an ion). therefore, the statement can indeed be made that ions have an even number of valence electrons, ad a radical has an odd number.
things get a little more complicated when talking about transition metal ions since they always occur in complexes. for the example you cite, Fe2+, it has 6 VE. they can be either all paired up, or 4 unpaired(tetra radical). this is why you always see transition ions in complexes, most commonly with oxygen.
 
Carl F. 
Carl,
 
Actually, I mentioned both common ions of iron.  By your definition, though, Fe3+ is not an ion, correct?  Or maybe it is a "radical ion"?  The point I am trying to make in this thread is that no good "cut-and-dry" rules or maxims can be given which do not admit exceptions, largely because of the transition metals and their ions.  If we count Fe3+ as a radical, or maybe a "radical ion", do we gain any clarity?  Clarity can only be achieved by knowing the quantum rules involved.  In fact, we ought to count both as ions, but know the exceptional status of Fe3+ with respect to the maxim "all ions have all their electrons paired." 
-HH-

Comment

Oops.  Did it again.  That should have been added as an answer, rather than a comment.  Too bad I can't remove, or even edit my comment.

I would state that Br is a free radical because it has an unpaired electron and an equal number of protons and electrons in the valence.  Br- is an ion because it has 1 more electron than protons in order to follow the octet rule.