Here's why:

* Electron Configuration: Xenon's electron configuration is [Kr] 4d¹⁰ 5s² 5p⁶.

* Valence Electrons: Valence electrons are the electrons in the outermost energy level of an atom, which are involved in chemical bonding.

* Group 18: Xenon belongs to Group 18 (Group VIIIA) of the periodic table, also known as the noble gases. All noble gases have a full outer shell of electrons, making them very unreactive.