Identify the element’s symbol and atomic number (Z)
Determine the group number (main-group elements):
Group 1 → 1 valence electron
Group 2 → 2 valence electrons
Group 13 → 3 valence electrons
Group 14 → 4 valence electrons
Group 15 → 5 valence electrons
Group 16 → 6 valence electrons
Group 17 → 7 valence electrons
Group 18 → 8 valence electrons
For ions:
Add 1 valence electron for each negative charge
Subtract 1 valence electron for each positive charge
For transition metals:
Use the valence electrons from the n s and (n − 1) d orbitals (common approach: group/oxidation-state dependent)
For representative elements using electron configuration:
Write the electron configuration
Count electrons in the highest principal energy level (largest n) as valence electrons
If given an electron configuration directly:
Count electrons in the outermost shell (highest n)
For main-group atoms with full shell:
Group 18 elements have 8 valence electrons (except He has 2)