Periodic Table Question

On most of the the Periodic Tables that I have seen the groups or column will have a number followed by an A or B what does this mean? Also there are 3 columns elements that are under the VIII A grouping, why is this? Thank you in advance for helping to dispell my igonorance.

To put it bluntly, those As and Bs are more or less arbitrary assignemnts. Silly chemists… Anyway, Web Elements has a brief explanation on this subject.

By the way, I have no idea why there are three columns under the VIII A/B groups. My guess is that it’s another one of those archaic conventions in chemistry. You might want to try looking up its origins from those references listed at the end of that Web Elements page.

This Periodic Table lists 2 different group numbering systems, with the American System being show in both Roman and Arabic numerals.

As to groups 8, 9, and 10 being grouped together in both the American and British system, a WAG: All three of the elements at the top – iron, cobalt, and nickel – are magnetic in their pure form. (Alnico alloy is also magnetic, though I don’t know if the aluminum in it helps in its magnetism as a whole or if it’s there to make it more ductile.)