Question

the compound of Xenon with zero dipole moment is?

Answer 1

Two things to consider here: the identity of the substituents and their arrangement around the central atom (Xe).

Using VSEPR you should be able to develop ideas of the arrangement of atoms for each structure... however, things get complicated for XeO2. For example, XeF4:

Xe has 8 electrons available for bonding. Covalent bonds to 4 fluorines will leave two lone-pairs of electrons on Xe. These lone pairs will want to be as separated as possible, forcing the four substituents into a plane. XeF4 is therefore said to be square planar (check out the wikipedia article on Xenon tetrafluoride for a picture).

A zero dipole moment results when the various dipoles of the bonds in the molecule cancel eachother out. This requires symmetry, which we have in abundance in XeF4. Each Xe-F bond has an identical dipole, but each as cancelled out by the bond opposite it, so the sum of dipoles from Xe-F bonds is zero. Also we need to consider the lone pairs, but as noted earlier, they are directly opposed to eachother so it follows that they will cancel eachother out too.

So, XeF4 is the answer. Check out the pictures of all the other molecules on Wikipedia (maybe try to work out what they'll be first), and you should be able to rationalise why all the other answers are wrong! :)