Which element is most likely to be a nonreactive gas?

A) Cs, number 55

B) Xe, number 54

C) F, number 9

D) Na, number 11

Xe

Explanation:

Cs and Na are solids in room temperature while F and Xe are gases.

The number of electrons in the outermost shell of an atom will determine its reactivity. Out of the gases given Xe and F, F (the most electronegative element) posses 5 valence shell electrons which makes it highly reactive while Xe which is a noble gas posses 8 valence shell electrons which makes it less reactive compared to many elements.