Find the element’s group on the periodic table
Determine the number of valence electrons
Use the tendency to gain or lose electrons to reach a full outer shell
Metals usually lose electrons and form positive ions
Nonmetals usually gain electrons and form negative ions
The ion charge equals the number of electrons lost or gained
Group 1 elements form 1+ ions
Group 2 elements form 2+ ions
Group 13 elements form 3+ ions
Group 15 elements form 3- ions
Group 16 elements form 2- ions
Group 17 elements form 1- ions
Transition metals can have multiple possible charges
Use the compound’s overall neutral charge to solve for an unknown ion charge
Write the ion with its charge as a superscript, such as Na+ or Cl-