Which of the following species are isoelectronic? Select all that apply.

Question

1) S^2-
2) Be^2+
3) Cl^-
4) K^+
5) Ca^2+
6) Se^2-

Answer 1

Isoelectronic means the same number of electrons.
I would suggest you write out the electron configuration of each, then compare. For example, #1 is
16S = 1s2 2s2 2p6 3s2 3p4; therefore,
take away two outside electrons and
16S^-2 becomes 1s2 2s2 2p6 3s2 3p2
etc.

Answer 2

For S^2- why are taking away electrons? Are suppose to add electrons?

Answer 3

So far I have S^2-, Cl^-, K^+, and Ca^2+ instead the other two as the answer. Please tell me if I have these answers correct.