This page is an exercise in relating the number of protons, electrons and neutrons for an atom or monoatomic ion. When you press "New Problem", an atomic symbol will appear in the first cell and several other cells will have values. Fill in the empty cells (all of the values are integers) and press "Check answer." Results appear in the smaller table. You need a periodic table or a list of the elements to use this page. If the charge is positive, just enter the integer. If it's negative make sure you include the sign.