There's a little more to consider here! First, consider how the molecules could be connected, given what you know of how different elements behave. You should, at this point, know that carbon tends to get in the middle of things, fluorine always gets on the outside, and sulfur can either get in the middle (particularly surrounded by oxygen!), on the outside, or occasionally in the middle but surrounded by other things than oxygen.
Here, since for C + 4F, carbon must be in the middle, the carbon shares each of its 4 valence shell electrons (it starts out as 2s(2), 2p(2); but then the electron distributions mix around "hybridize" to form four equivalent single sp(3) type electrons, directed out towards the corners of a tetrahedron (triangular pyramid)). Each of the F atoms shares one of its 2p electrons with the carbon. NOW you have four rather polar bonds (the fluorine has more of its shared electron pair, and the carbon has less of it), but since the bonds are directed symmetrically outwards, there's no net dipole moment to the molecule, as noted in the answer above.
For CS(2), the carbon still has 4 electrons to share "out", and needs 4 electrons shared "in"; each of the sulfurs needs to share 2 electrons "in". So, the carbon shares its two pairs of electrons "out", either direction along an straight axis going through the carbon nucleus, and one sulfur atom perches to either side of the carbon. Technically, one pair of electrons between the carbon and a sulfur are a "sigma bond" -- the electrons are in a cloud centered right along the axis. The other pair of electrons between each carbon and the sulfur are found in a "pi bond" -- they are found in two banana-shaped regions, one region on either side of the axis, but *not* along the axis itself. More interestingly, the pi-bonds going out towards the two sulfur atoms, are not lined up with each other; rather, they are turned 1/4 turn away from each other, as you view them down the axis. Why do they do this? B/c they need to get as far away from each other as possible, and that's the position that gets them there.
Again, although each of the carbon-sulfur bonds (considering the sigma and pi bonds between each carbon-sulfur pair as grouped together for charge effect) is rather polar (though not as polar as a carbon-fluorine bond!), b/c the 2 bonds are going in exactly opposite directions, the total molecule as a whole is non-polar.
Why is this polar vs. non-polar characteristic of a molecule important?
B/c polar molecules boil at much higher temperatures than non-polar ones. CF4 boils ~ -127C; CS2 (being much heavier from the S's) boils at 46C. But a little POLAR molecule like H2O -- boils way up at 100C. If it didn't have hydrogen bonding (as a result of its polarity) it would boil way low -- maybe -100C {comparators: H2Se @-41C, H2S @-60C} -- and life as we know it wouldn't exist!
Even if we didn't have to worry about our existence, it's also certainly easier to work with solids and liquids in the lab, rather than gases that are always trying to escape and diffuse away! So, predicting the physical characteristics of new materials is a very useful thing to be able to do.
