Which pair of noble gases is explicitly known to form chemical compounds with fluorine and oxygen?

The correct option is Krypton and Xenon.

Explanation

Noble gases (Group 18) possess a stable octet configuration ($ns^2np^6$), resulting in very high ionization enthalpies and general chemical inertness. However, heavier noble gases have lower ionization enthalpies, allowing them to react with highly electronegative elements like fluorine and oxygen to form chemical compounds.

Analysis of Reactivity:

• Xenon (Xe): Due to its larger atomic size and lower ionization enthalpy, Xenon forms the widest range of stable compounds. Common examples include fluorides ($XeF_2, XeF_4, XeF_6$) and oxides ($XeO_3$).
• Krypton (Kr): Krypton is less reactive than Xenon but forms compounds such as Krypton Difluoride ($KrF_2$).
• Helium (He), Neon (Ne), and Argon (Ar): These lighter noble gases have extremely high ionization enthalpies. They do not form stable chemical compounds under standard conditions.
• Radon (Rn): Radon forms fluorides (e.g., $RnF_2$), but it is radioactive. However, options containing Argon or Neon are incorrect because those specific elements are chemically inert.

Conclusion:
Krypton and Xenon are the only pair listed where both elements are explicitly known to form stable chemical compounds.

Key Takeaway:
Chemical reactivity in Group 18 increases down the group as ionization enthalpy decreases. Xenon and Krypton are the primary noble gases capable of forming compounds, specifically with strong oxidizing agents like fluorine and oxygen.