Question

Sort these elements into isoelectronic groups. Into three different boxes/sections.

Elements:
F-
O2-
Al3+
S2-
Ti4+
K+
He
Li+
B3+

Answer 1

David, you must be having an identity crisis.
Isoelectronic means the same number of electrons The easy way to do this is to write the electron configuration for each, then count to see which ones are in each "box" of the same number of electrons.
9F^- means 10e = 1s2 2s2 2p6
13Al^3+ means 10e = 1s2 2s2 2p6
So these two are isoelectronic (and there could be another with 10e. If so that would be isoelectronic with these two also). The others are done the same way.

Answer 2

Nope, just working in a study group. Each person asking a question. Thanks for the help. I thought about doing something like that but I was writing them with the noble gas first and that was making it difficult to see the pattern.