Check the element’s group on the periodic table
Determine whether it is a metal, nonmetal, or noble gas
Use common ion charges by group
Group 1 elements: +1
Group 2 elements: +2
Group 13 elements: +3
Group 15 elements: -3
Group 16 elements: -2
Group 17 elements: -1
Group 18 elements: 0
Transition metals: check the specific element or compound
Use the octet rule to see how many electrons are gained or lost
For atoms in compounds, use oxidation states
For polyatomic ions, use the ion’s known overall charge
Verify the charge by balancing the total charge in the formula