Which part of the periodic table are the elements at the top of the activity series in?
Here is a picture of the activity series.
The top seven elements in the list are Li, Na, K, Mg, Ca, Sr, and Ba. These are all in Groups 1 and 2 of the Periodic Table.
This makes sense because they can get a stable octet by losing only one or two electrons. So they are reactive elements.
Hope this helps.