Source: http://web.a9lame.com/Documents/Lyc%C3%A9e/Bac%20FR/a-Tronc%20commun%20International/a-Tronc%20commun%20Science/c-Chimie/a-Semestre%20I/f-Classification%20p%C3%A9riodique%20des%20%C3%A9l%C3%A9ments%20chimiques/a-Cours/Cours%207%20Classification%20p%C3%A9riodique%20des%20%C3%A9l%C3%A9ments%20chimiques.pdf