Categorize each of the following four examples of isomerism as either structural isomerism or stereoisomerism [ster-ee-oh-EYE-suh-mer]: geometrical; ionization; polymerization [puh-lim-er-uh-ZAY-shuhn]; optical.
STRUCTUREI ISOMERISM: 2, 3 (IONIZATION, POLYMERIZATION); STEREOISOMERISM: 1, 4 (GEOMETICAL, OPTICAL)