# Acids of noble gases

Are there any other acids of noble gasses besides xenic acid? Why other ones seem to be very unstable (like perxenic), or completely unknown (acids of any other noble gases). Particularly are there fluoroxenic acids, for example $$\ce{HXeF5}$$?

• I rewrote your question. Check out if the changes are OK for you. – Mithoron Sep 29 '18 at 15:51
• You don't make clear if Lewis acids are acceptable - if so XeF6 is an example in its reactions with CsF. – Ian Bush Oct 1 '18 at 10:46
• I want them to be h+ donor not lewis acids – Harsh jain Oct 1 '18 at 14:56

Yes there is and it has a very simple structure and is the strongest acid known: HeH$$^+$$. You might find it interesting to know that HeH$$^+$$ is also most likely the first molecule to have formed after the Big Bang.

• Is it stable i don't think so and acc. to me strongest acid is fluoriantimonic acid – Harsh jain Oct 1 '18 at 2:18
• Can it protonate fluoriantimonic acid – Harsh jain Oct 1 '18 at 3:49
• It's stable in vacuum and it is not really an acid in the classical sense as you cannot really make a solution of HeH$^+$. See also the discussion here. – Paul Oct 1 '18 at 8:57
• Has it ever been created in pure has phase in space or vaccum chamber – Harsh jain Oct 1 '18 at 9:41
• It has been created in the laboratory in He plasma's around 1925. Though many people think it should have played an important role in the early Universe, it has no been detected there yet. A possible reason might be its high reactivity so that it may only be detected at very high redshift when there were no neutral particles to accept its proton (He was the first element to become neutral in the post-Big-Bang plasma). – Paul Oct 1 '18 at 12:43

An acid of krypron is also known and its barium salt is known to be stable. From an abstract of a 1964 paper:

An acid of krypton is formed when krypton tetrafluoride is slowly hydrolyzed by ice at -30 degrees to -60 degrees C. The yield is 2 to 3 percent (mole). A barium salt of this acid, thermally stable at room temperature, is formed by the hydrolysis of krypton tetrafluoride with a 0.35N solution of barium hydroxide at O degrees to 5 degrees C in a yield of approximately 7 percent by weight.

• Hmmmmm ... According to wikipedia at least the "discovery" of KrF4 was shown to be mistaken (en.wikipedia.org/wiki/Krypton_difluoride), thus throwing doubt on the formation of Kryptic acid. Can't find a better reference before I rush out, anybody? – Ian Bush Oct 1 '18 at 7:47
• – Nilay Ghosh Oct 2 '18 at 4:52