Find the element’s symbol on the periodic table
Read the atomic number listed for that element
Count the number of protons in the nucleus
Use the number of protons as the atomic number
For a neutral atom, use the number of electrons only if the proton count is already known
For ions, ignore the charge and still use the proton count
If given isotopes, use the element identity, not the mass number
If given an atomic structure diagram, count the protons in the nucleus
If given the electron configuration, identify the element and match it to the periodic table
If given the periodic table position, the atomic number is the whole number assigned to that element