I've been reading Wikipedia's article on $\ce{NI_3}$ (which doesn't contain an $\ce{I_3^-}$ ion, so "nitrogen III iodide" would probably be a better name for it) and getting very confused. I'll start by distinguishing the decompositions$$\begin{align}2\ce{NI_3}&\to\ce{N_2}+3\ce{I_2},\\8\ce{NI_3NH_3}&\to5\ce{N_2}+6\ce{NH_4I}+9\ce{I_2},\end{align}$$since $\ce{NI_3}$ is often isolated or stored in the form $\ce{NI_3NH_3}$. Here are the two things I'm confused about:

  • "Nitrogen triiodide was first characterized by Raman spectroscopy in 1990 when it was prepared by an ammonia-free route", despite at least one paper on experiments with nitrogen triiodide dating to 1958. I assume previous experiments were instead by the ammonia route.
  • Now for the real mystery. Apparently, alpha radiation can trigger such a decomposition (according to Bowden 1958, so presumably it's the second reaction). Someone has earned a "citation needed" for adding, "several attempts to replicate this action have failed".

So here are my questions:

  • How confident are we that alpha radiation has the claimed effect?
  • What mechanism, be it purely theoretical or empirically mandated, has been proposed for such a decomposition? (See also my discussion below with @IvanNeretin of its attribution to the high KE of alpha particles.)
  • 4
    $\begingroup$ You have a rather distorted perspective of the whole "chemical vs nuclear" picture, as if looking at it from the wrong end of a telescope. Electronegativity of He does not matter. Charge on He does not matter (well, almost). Helium chemistry is not a part of the picture. What matters is the energy of an alpha particle, and the energy is really, really big, and even bigger than that. $\endgroup$ Sep 22 at 15:13
  • $\begingroup$ @IvanNeretin Are you saying the mechanism is that the alpha's multiple-MeV KE allows it to break covalent bonds? If so, does alpha radiation cause many materials to decompose? $\endgroup$
    – J.G.
    Sep 22 at 16:02
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    $\begingroup$ Yes, very much so. It is just that your wording, while technically correct, is a massive understatement, as in "High energy of a nuclear explosion may result in property damage, if performed indoors". Indeed, radiation of any type would gradually destroy many materials, and naturally, those which tend to decompose by themselves are the most vulnerable. $\endgroup$ Sep 22 at 16:12
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    $\begingroup$ A typical chemical bond is about 2-4eV. A Typical alpha particle has about 5,000,000eV KE (en.wikipedia.org/wiki/Alpha_decay). You are asking "If somebody drops a nuke on my house can you tell me where the bricks will land" $\endgroup$
    – Ian Bush
    Sep 22 at 17:06
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    $\begingroup$ chemistry.stackexchange.com/questions/107151/… $\endgroup$
    – Mithoron
    Sep 22 at 17:19

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