In XeF2, the oxidation number of xenon (Xe) can be determined as follows:

Let x represent the oxidation number of Xe. Since fluorine (F) has an oxidation number of -1 in most compounds:

2(-1) + x = 0

Solving for x:

-2 + x = 0

x = +2

Therefore, the oxidation number of xenon in XeF2 is +2.