The missing Xe(IV) oxide, XeO2, has been synthesized at 0 degrees C by hydrolysis of XeF4 in water and 2.00 M H2SO4(aq). Raman spectroscopy and O-16/18 isotopic enrichment studies indicate that XeO2 possesses an extended structure in which Xe(IV) is oxygen bridged to four neighboring oxygen atoms to give a local square-planar XeO4 geometry based on an AX(4)E(2) valence shell electron pair repulsion (VSEPR) arrangement. The vibrational spectra of (XeO2)-O-16 and (XeO2)-O-18 amend prior vibrational assignments of xenon doped SiO2 and are in accordance with prior speculation that xenon depletion from the Earth's atmosphere may occur by xenon insertion at high temperatures and high pressures into SiO2 in the Earth's crust.