# Why can't helium nuclei (alpha particles) react with fluorine?

Alpha particles are basically just helium nuclei, so it will accept an electron pair to become stable.

Will fluorine, being highly electronegative, not just donate an electron pair but form a bond with helium?

• So are you asking about the existence of $\ce{HeF2}$?
– bon
Sep 13 '15 at 13:48
• Don't confuse the extreme nuclear stability of the $\cf{^4He}$ nucleus, i.e., an alpha particle, with the electronic stability of naked $\cf{He2+}$ cations. Sep 13 '15 at 13:55
• Nobody said a word about $\ce{He}_2^+$; as for $\ce{He}^{2+}$, it is of course electronically stable, as it has no electrons at all. Sep 13 '15 at 13:56
• @marcus - Please edit your question for clarity and content. As it stands, it's very unclear what you are asking and might get closed. Sep 13 '15 at 13:57
• How could it not be? Imagine a lone alpha particle deep in outer space; how is it unstable? What would happen to it, electronically or otherwise? (Sorry, just kidding.) Sep 13 '15 at 14:06

Why, many atoms would readily create a bond with helium, when it comes in a form of alpha particle (just cooled down enough to chemically interact with). There is comparatively stable $\ce{HeH}^+$ and other similar particles, too. But a positive particle is not a compound yet. And when you try to form a compound out of it, that is, to balance it with some negative ions - well, that's where the problem arises. It would violently react with absolutely anything else, form some compound, and happily release the neutral helium atom.

• Thats why i asked what if alpha particles were to form bonds with fluorine? In a case like that the alpha particles couldn't just take away the electrons of fluorine and leave a positively charged fluorine? Sep 13 '15 at 14:28
• Of course it can. The ionization energy of helium is by far the largest among all elements, so it will take electrons from anything. A covalent bond may be formed, too; I expect a particle like $\ce{HeF}^+$ to appear, which would be stable for just as long as it doesn't encounter anything negatively charged. Sep 13 '15 at 14:42
• You mean as long as long as it does not encounter anything, except another Helium atom, right?
– Karl
Sep 13 '15 at 23:38
• I said "negatively charged". Come to think of it, most neutral particles (except another helium atom, you are right on that) would react with it just as well. Positive ions, though, probably would not. Sep 14 '15 at 7:15

Will fluorine, being highly electronegative, not just donate an electron pair but form a bond with helium?

Yes a fluorine atom and helium atom can form a "molecule" $\ce{HeF}$. Such a molecule would be very unstable chemically. Two such molecules bumping into to one another would yield helium atoms and fluorine molecules.

An alpha particle is an "energetic" bare helium nucleus. Think of the speed that a fluorine molecule would be moving in fluorine gas. The charged alpha particle is traveling much much faster so it is ripping through the gas bumping into fluorine molecules thus creating ions and free electrons. So in fluorine gas as the alpha particle slows down it forms a helium atom. Thus overall you'd get uncharged helium atoms and $\ce{F2+}$ ions.