In organic chemistry course, I read that a radical is an atom, molecule or ion which have unpaired valence electrons.

So does there any difference between chlorine atom or cholrine radical? Also sodium atom contains one valence electron which is unpaired, then does sodium atom is also considered a radical? Please clarify it.

  • $\begingroup$ There is a difference. Neither sodium, nor chlorine radical needs to be a single atom. The may be who knows how many polyatomic species that can be called like that. $\endgroup$ – Mithoron Apr 19 '20 at 17:03
  • $\begingroup$ In organic reactions, I studied that Cl-Cl bond breaks homolytically to form two Cl radicals. I am not able to understand your statement. Please explain it more for better clarification. $\endgroup$ – Manu Apr 19 '20 at 17:10
  • $\begingroup$ Many radical cations of chlorine were detected. en.wikipedia.org/wiki/Polyhalogen_ions Not to mention monoatomic cation radicals, and excited states. $\endgroup$ – Mithoron Apr 19 '20 at 17:20
  • $\begingroup$ I upvoted your question because I had to employ one of my recent Question on SE as a source. I knew the material I provided, although not well received per votes cast, was and may continue to be, a cited source. Thanks. $\endgroup$ – AJKOER Apr 19 '20 at 19:30

Yes, a chlorine atom is very much the same as chlorine radical.

With sodium, the two things are technically similar too, but you'll hardly ever encounter a mention of "sodium radical".

Why is that? Well, I guess there is a difference between Na and Cl. A chlorine radical exists in its own right (if only briefly), and is an important intermediate in many reactions. A sodium radical, on the other hand, is pretty much not a thing. Single sodium atoms just don't wander around alone. You may see reactions involving metallic sodium, or ionic salts of sodium, or maybe (not sure about that) some compounds which can pass for covalent, or (unlikely) even $\rm\bf Na^{\pmb-}$... but that would be all.

So it goes.

  • $\begingroup$ Although I get your point, I have seen something like sodium radicals in SET mechanisms like this one for the Wurtz reaction. Doesn't it count for something? $\endgroup$ – Yusuf Hasan Apr 19 '20 at 9:24
  • $\begingroup$ Maybe it does (that's why I said "hardly ever", and not "never"). Or maybe it is just a metaphor of metallic sodium. $\endgroup$ – Ivan Neretin Apr 19 '20 at 9:30
  • $\begingroup$ \rm\bf Na^{\pmb-} — seriously?! $\endgroup$ – andselisk Apr 19 '20 at 11:20
  • $\begingroup$ @andselisk Why not? Alkalides are a thing. $\endgroup$ – Ivan Neretin Apr 19 '20 at 11:32
  • $\begingroup$ @IvanNeretin I'm referring to the pornographic *TeX syntax:) $\endgroup$ – andselisk Apr 19 '20 at 11:35

While I essentially agree with the statement that one generally does not differentiate between the chlorine atom and the chlorine radical, this is not the case with hydrogen.

In fact, while the hydrogen atom and hydrogen radical (also called, per a recent thread question of mine, as Hchemisorbed (per my provided answers available here), I also noted in that question's answer that there exists, so-called 'atomic hydrogen', distinct from $\ce{.H}$, which is a fleeting very high energy state of hydrogen created in an electric arc (actually commercially employed in high-temperature welding, see here).

So, in general, depending on the element, the answer actually appears to be mostly yes but sometimes no.

  • $\begingroup$ So can we conclude that every atom, or molecule containing unpaired electron is radical but we can use other terminology for them depending on the method they are prepared ( like "atomic Hydrogen" when H radical is formed by electric arc or "Nascent Hydrogen" when H radical is produced in a reaction)? $\endgroup$ – Manu Apr 19 '20 at 16:55

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