Now, whenever we have the two HS on the same side of the plane, or the x and Y, the heavier atoms on the same side of the plane, we have CITs or Z compounds or molecules. In other words, we define C compounds as hydrogens being on the same side. And we define Z compounds as having the heavier groups on the same side. Remember, we define x and Y to be any compound, molecule or atom that is different than H. And that means our x and Y are both heavier than H's. So this compound is one isomer of this molecular formula and it's the sys or Z isomer. What about trans or e?