Understanding the Placement of Lanthanides and Actinides on the Periodic Table

[GotMex?]

I'm designing an online periodic table of the elements and I have a question about the lanthanide and actinide families. I notice that all periodic tables put them below the main table, aligned with groups 4-18. Does this mean that they fit into those groups? Or is it just placed like that to look neat.

I'm thinking that they are not part of those groups since a table I found with inline F-block elements shows them as not being part of them. I wish I could recall my chemistry courses' teachings but it was a while ago so I can't remember. I just wanted to make sure before I continue since depending on the answer, my design will vary a bit. Thanks.

Here's a link to a table so you don't have to search for one: http://en.wikipedia.org/wiki/Periodic_table_%28standard%29"

 

[dmoravec]

much like there is a gap between magesium and aluminum there is a gap between stronium (Sr) and yttrium (Y) but instead of making the periodic table really wide they put that section below the rest of the table. When talking about groups I believe that generally they are not included with any group (except I have seen Lanthanum and Actinium in group 3) since they are mostly rare elements and many are unstable. The groups are generally used as a rough comparision between elements for reactions and such stuff, but those elements tend not to follow any general pattern. If they were labled as groups it would probably be 3A, 3B, etc starting with Cerium and Thorium.

 

[GotMex?]

Sweet, thanks for the info. This should make for a harder to design CSS periodic table hehe. I was hoping i was going to be able to just group them into the other groups... oh well.

 

[Astronuc]

Here is the extended version - wide.

http://en.wikipedia.org/wiki/Periodic_table_(extended)

or

http://www.webelements.com/