Xenon is by far the most chemically reactive noble gas, owing to its comparatively low first ionisation energy. Direct reaction with fluorine gas over a nickel catalyst at 400 °C gives, depending on the Xe:F2 ratio and pressure, XeF2 (1:1), XeF4 (1:5, over Ni/acetone) or XeF6 (1:20, 200 atm). Heating XeF6 in a sealed quartz vessel at 50 °C progressively substitutes oxygen for fluorine via the quartz itself (2XeF6 + SiO2 -> 2XeOF4 + SiF4, then onward to XeO2F2, then XeO3); complete hydrolysis of XeF6 with water similarly gives the explosive solid XeO3 directly (XeF6 + 3H2O -> XeO3 + 6HF). Treating XeF6 with 2.5 M NaOH gives sodium perxenate (2XeF6 + 16NaOH -> Na4XeO6 + Xe + O2 + 12NaF + 8H2O), whose perxenate ion (XeO6^4-) is such a strong oxidant it converts Mn2+ directly to permanganate without a catalyst. Xenon also reacts directly with PtF6 to give the orange-yellow adduct [XePtF6] — historically the first noble-gas compound ever made (Bartlett, 1962) — and its fluorides act as fluoride-ion acceptors toward strong Lewis acids like SbF5/TaF5, forming add …