 So far, we've just looked at chains of carbons, but it's also possible to make rings. If you take a straight chain alkane, like propane, and curl its ends around and join them together, you have cyclo-propane. The formula for propane is C3H8. The formula for cyclo-propane is C3H6. Try to convince yourself why this is. Remember that carbon forms four bonds. When you get your hands on some molecular modeling equipment, you can try it out for yourself. The names of these cyclo-alkanes follow the same pattern as ordinary alkanes. The suffix AIN shows you that it's saturated. It only has single bonds. The middle part of the name is the bit that tells you how many carbons are in the ring, and the extra cyclo at the front indicates that the molecule is in a ring rather than a chain. Here are some more cyclo-alkanes, and here's how we draw them as stick structures. And this is the formula for a general cyclo-alkane with N carbons.