Final answer:
A 'Structural formula in organic chemistry' is not analogous to the concept of a unit cell in crystal structures, because it represents a unique arrangement within a molecule, not a repeating pattern forming a larger structure.
Step-by-step explanation:
In the context of crystal structures, a unit cell is the smallest repeating unit that depicts the entire crystal's three-dimensional arrangement. Analogous to a unit cell are elements that can be repeated to form a larger structure. Given the analogies, 'Structural formula in organic chemistry' is NOT analogous to the unit cell concept. Unlike a unit cell which repeats to form the solid structure, a structural formula represents the arrangement of atoms within a molecule and is unique to that compound. On the other hand, a 'Pixel in a digital image' and a 'Tile in a mosaic' serve as direct analogs as they are repeated to create a larger image or pattern, similar to how unit cells repeat to form a crystal lattice. 'Chapter in a book', while a repeated structure within a book, does not represent an identical repeating pattern that constitutes the whole, making it less analogous.