Final answer:
Building a model of salt using marshmallows and toothpicks can be challenging due to accurately representing the atom sizes and bonding, as well as the crystal lattice structure.
Step-by-step explanation:
Building a model of salt using marshmallows and toothpicks can be challenging due to a few reasons. First, accurately representing the size difference between sodium and chlorine atoms with regular-size and mini marshmallows may not be easy.
Second, ensuring the toothpicks connect the marshmallows in a way that accurately represents the bonding between the atoms can be tricky. Lastly, building a model that accurately reflects the crystal lattice structure of sodium chloride may require careful arrangement and precise positioning of the marshmallows and toothpicks.