[Asian_pride]

What's the difference between

• Group 11 and A? Why do they have to make them different?
  3A and 3B? Why doesn't 3B come first?

[KurzickMushroom]

A and B tells you what type of element it is. Group A are the representative elements. Group B are the transition metals. I also think only group B can have multivalent elements. The number itself is the the number it is given when you count left to right on the Table. With representative metals, the number also tells you the number of valence electrons elements in that row have so...1a has 1 electron, 2a has 2, 3a has 3.

Hope this helps.

[Vidya]

Hi
periodic table is very highly organized and systematic arrangement of elements.It based on very fundamental and simple concept of electronic configurations.so elements with same electronic configurations are placed together .So it makes it very clear that you can   not shift positions of these groups and elements as you want.They have fixed groups and periods because they have fixed electronic configurations.

[cliverlong]

What's the difference between

• Group 11 and A? Why do they have to make them different?
  3A and 3B? Why doesn't 3B come first?

I believe there have been different numbering of groups in the periodic table particularly where s- and p- block elements were numbered 1 to 8 with an A suffix and the d-block elements numbered with a B suffix. But different systems employed contradictory uses of the suffix A and B

I believe the following to be the current IUPAC approved numbering of groups that does away with A and B suffixes

http://old.iupac.org/reports/periodic_table/IUPAC_Periodic_Table-22Jun07b.pdf
http://www.webelements.com/

the new (current) numbering now does not give you direct information about "outer shell" electrons for s- and p-block elements.

Look here

http://en.wikipedia.org/wiki/Chemical_series

for a mapping between various old systems and the current IUPAC numbering of chemical groups.

Clive