Question

The ion that has the same e- arrangement as Ar:

A k+
B CL-
C S2-
D Ca2+
E all of these

Answer 1

Well, I recommend reading the text :P

Answer 2

the answer is E- all of these

to check if these ions have the same e- configuration, check them in the periodic table and see where they land when you take or add electrons.

for example, K is one space away to be like Ar, which is just one space behind. having a positive charge +1, means that it has one less electron. if you remove this electron, it is like Ar because is one space.

another example-> S-2 means you have add two electrons because charge is negative, so you add. two spaces after S land in Ar. so it is same e- configuration as Ar.