I've just begun reading about halonium ions and I noted that only the first four halogens are acknowledged to be able to form halonium ions, but hydrogen astatide can be formed.
I can't seem to find any answers on the internet, but knowing that astatine is super reactive and radioactive, I suppose it may be due to this that forming an "astatonium" molecule would be nearly impossible?
On the Wikipedia entry of hydrogen astatide, it states that there is an astatonium — listed as a conjugate acid. However, a quick Google search of the term astatonium only reveals 14 results.