The basic knowledge of chemical formula writing is fundamental for chemistry students, yet many still struggle to learn it. To provide a more interactive and engaging approach that facilitates and reinforces student understanding of chemical formulas and stoichiometry of chemical reactions, we have designed a chemical jigsaw puzzle. Only eight general jigsaw puzzle shapes are needed to represent atoms (e.g., H, C, N, O, X, ···) or groups (e.g., -CH[subscript 3], Et, But, Ph, ···), shared electrons in covalent bonds, lone pairs, and unpaired electrons for radical compounds. The complementarity of the chemical jigsaw puzzle pieces can present a large variety of molecular arrangements with several functional groups, including radical and ionic species. Thus, concepts such as organic functions, resonance, hybridization, Lewis dot structures, octet configuration, formal charges, stoichiometry, and others can be readily exemplified. Its use is intended for introductory chemistry courses, especially in high school. The usefulness and effectiveness of this chemical jigsaw puzzle was checked in the classroom throughout a hands-on learning activity using medium-sized pieces, built with low-cost material.