Inorganic substances are relatively simple, so they can be described with simple formulas that show only the number and type of atoms in a compound. Organic compounds are complex, and are described, instead, with structural formulas that show the arrangement of atoms in a compound. This is necessary because there is often more than one arrangement for the atoms of organic compounds that share the same simple formula. Compounds with the same simple formula but different structures are called isomers. This PowerPoint presentation describes structural and graphic formulas. It also explains how to recognize isomers. Worksheets on this topic are available free of charge on my website at www.evanschemistrycorner.com.