those resources don't really answer the question I'm asking. I can't find out why the structural formula and chemical formula don't have the same number carbons and hydrogens, but when I added both sides of the structural formula they do add up. CH2O2C6H3CH2CH=CH2: Left side has a total of 9C 8H O then add it to the right side with 1C 2H = chemical formula C10H10O2. The structural formula for this compound is made the same way as other compounds except you remove CH2 from it and set it equal to it, just not sure why they removed the CH2 and set it equal to it.