Final answer:
Glucose, galactose, and fructose have the same chemical formula but are structural isomers with different arrangements of atoms; glucose and galactose are aldoses, while fructose is a ketose.
Step-by-step explanation:
The molecular formula for glucose, fructose, and galactose is C6H12O6. Because they all have different molecular structures, they are known as structural isomers. Structural isomers are compounds that have the same chemical formula but atoms are bonded to each other in a different arrangement. Glucose and galactose are classified as aldoses, and fructose is known as a ketose. This variation in structure leads to differences in their physical and chemical properties even though they share the same molecular formula.