Find the element’s group 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
Group 13 elements have 3 valence electrons
Group 14 elements have 4 valence electrons
Group 15 elements have 5 valence electrons
Group 16 elements have 6 valence electrons
Group 17 elements have 7 valence electrons
Group 18 elements have 8 valence electrons
Helium has 2 valence electrons
For transition metals, use the outermost s electrons and sometimes d electrons depending on the context
Write the electron configuration and count the electrons in the highest principal energy level
The highest-energy outer electrons are the valence electrons
For ions, add electrons for negative charge and subtract electrons for positive charge before counting valence electrons