Which of the following does not exist ?

(i) XeOF₄

(ii) NeF₂

(iii) XeF₄

(iv) XeF₆

The sum of first and second ionization enthalpies of Ne are much higher than those of Xe. As a result, F₂ can oxidise Xe to Xe²⁺ but cannot oxidise Ne to Ne²⁺. In other words, NeF₂ does not exist. In constrast, all the xenon flurides (XeF₄ and XeF₆) and xenon oxyfluoride (XeOF₄) do exist.