this organic chem first semester stuff, but my friend just confused me and I just wanted to make sure that I understand this correctly ethylene is 2 C double bonded  so 1,1,2,2-tetrachloroethylene would be 2 Cl bonded to a C=C which is bonded to another 2 Cl?  Or is it just single bonded? (You are correct, It is Cl2C=CCl2 - GS).