Find the element’s group number on the periodic table
For main-group elements, use the group number to determine valence electrons
Group 1 elements have 1 valence electron
Group 2 elements have 2 valence electrons
Groups 13–18 have 3–8 valence electrons
Subtract 10 from the group number for groups 13–18
Helium has 2 valence electrons
For transition metals, valence electrons are not always equal to the group number
Use the outermost electron shell to determine valence electrons for transition metals
Check the electron configuration if needed