Here's a digital activity to review atomic structure. Students will determine the number of protons, electrons, and neutrons in an atom; determine the number of electron shells and valence electrons, the atomic mass, and the atomic number. This self-grading activity has 16 questions and is available in Google Sheets and print; correct answers will turn green and reveal the hidden atom, and incorrect answers will turn red. This activity can be used as an assessment, a bell ringer, or exit ticket. Answer key is included.