Elements with similar chemistry are grouped together in 18 different groups, the number of which is called The group number. They are now numbered from 1 to 18, with hydrogen being in group 1 together with the alkali metals lithium, sodium, potassium, rubidium, caesium and francium; and with helium being in group 18 along with the other noble gases neon, argon, krypton, xenon and radon. In the old IUPAC system, the groups were labelled 1A, 2A, 3A, 4A, 5A, 6A, 7A, 8, 8, 8, 1B, 2B, 3B, 4B, 5B, 6B, 7B, and 0 respectively. In the Chemical Abstracts service Group notation they were labelled IA, IIA, IIIB, IVB, VB, VIB, VIIB, VIII, VIII, VIII, IB, IIB, IIIA, IVA, VA, VIA, VIIA, and VIIIA respectively. Naturally this led to great confusion!
This graph serves no useful purpose, as the information it displays is depicted in far better fashion by the periodic table itself. But it is extremely useful for plotting the properties of the elements on scattergrams with the group number on the x-axis.
