When you draw your Lewis Diagram, you just need to look off your periodic table to see how many valence electrons each atom will have. So: Cl=7 C=4 and H=1. Now that we know this, we can draw our diagram. The first carbon will bond with each of the chlorines, filling up their valence gaps, and the second carbon will bond with the two hydrogens, filling up their gaps. Now the carbons each have two electrons left to bond, so you can just draw a double bond between the two carbons, effectively using those extras up. Now you can see that on each of the carbons, their are no unpaired electrons, so we just look at how many arms the first carbon as…3, so it has the electron-group geometry of Trigonal Planar, as well as the molecular geometry of Trigonal Planar. The second carbon is the same story, it has 3 arms coming off of it, and no unpaired electrons, so its molecular and electron-group geometry will also be Trigonal Planar.