Completed example on an atomic structure worksheet showing calculations for Carbon-12.
A worksheet titled "Atomic Structure" with a table listing isotopes, atomic numbers, mass numbers, and other atomic properties. The first row for Carbon-12 (C-12) is filled out with handwritten red numbers: atomic number 6, mass number 12, 6 protons, 6 neutrons, and 6 electrons. A green arrow labeled "Mass #" points to the mass number. Red handwritten notes include "12-6=6" and "H" in the top right corner.