## Chemistry (7th Edition)

$C_{13}H_{18}O_2$ is the chemical formula for Ibuprofen
There are 13 gray spheres, so the formula has 13 carbons: $C_{13}$ There are 18 ivory spheres, so the formula has 18 hydrogens: $H_{18}$ There are 2 red spheres, so the formula has 2 oxygens: $O_2$