Ions: Isoelectronic series

Question

Considering only ions with charges of +1, +2, -1 and -2, or neutral atoms, give the symbols for 4 species that are isoelectronic with the barium ion, Ba²⁺.

Answer 1

Along with barium ion, Ba²⁺ , there would be; caesium ion, Cs¹⁺, xenon neutral, Xe, iodine ion, I^1- and tellurium, Te^2-.