Prasenjeet S.
asked • 08/04/13Difference 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?
More
4 Answers By Expert Tutors
Hassan H. answered • 08/04/13
Tutor
5.0
(176)
Math Tutor (All Levels)
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.
Beverly L. answered • 08/04/13
Tutor
5
(7)
Study Buddy
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.
Hassan H.
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-
Report
08/04/13
Carl F.
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.
Report
09/26/13
Hassan H.
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-
Report
09/27/13
Dick B. answered • 08/10/13
Tutor
4.9
(74)
Math and Science Tutor
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.
Becky F. answered • 08/04/13
Tutor
New to Wyzant
Honors and General Chemistry, Bio and Physical Science Teacher
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.
Still looking for help? Get the right answer, fast.
Ask a question for free
Get a free answer to a quick problem.
Most questions answered within 4 hours.
OR
Find an Online Tutor Now
Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.
Dick B.
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).
08/10/13