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 sulfide ion, S2-

Answer 1

When yoy say that one atom is isoelectronic with another one, means that both of those atoms have the same electron configuration.

In the case of sulfide ion, S^2- the 2- charge means that it has 2 more electrons in excess. So, if Sulfur has an atomic number of 16, with the 2 additional electrons, it will have an atomic number of 18 so:

[S] = 1s² 2s² 2p⁶ 3s² 3p⁴   This is the original configuration:

[S^2-] = 1s² 2s² 2p⁶ 3s² 3p⁶ This is the actual configuration of Argon (Z = 18) so, one of the atoms would be Argon (Ar).

Now for the other three we only need to find atoms with an atomic number near of 18, like Pottasium (19), Ca (20), Cl (17). But these atoms in it's neutral form it's not isoelectronic with the sulfide ion, so:

K⁺¹ means that we have to substract one electron of valence of it's configuration so:

[K¹⁺] = 1s² 2s² 2p⁶ 3s² 3p⁶   and the original configuration [K] = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

[Cl^1-] = 1s² 2s² 2p⁶ 3s² 3p⁶     and the original configuration [Cl] = 1s² 2s² 2p⁶ 3s² 3p⁵​

[Ca²⁺] = 1s² 2s² 2p⁶ 3s² 3p⁶  and the original configuration [K] = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

Hope this helps​