The period 3 element whose 2 - ion is isoelectronic with Ar is sulfide ion (S2− ).
What is isoelectronicity ?
Isoelectronicity is a phenomena that occurs when two or more molecules have the same structure (as in, the positions and connectivities between the atoms), the same electronic configurations, but differ by the individual elements that are present at particular sites throughout the structure.
For instance, while CH3COCH3 and CH3N=NCH3 are not isoelectronic, CO, NO+, and N2 are.
This concept is also known as valence isoelectronicity.
Sulfide, which has the chemical formula S2, is an inorganic sulfur anion or a compound that contains one or more S2 ions. Sulfide salt solutions are corrosive. The conjugate acids of sulfur are hydrogen sulfide (H2S) and bisulfide (SH).
To learn more about Sulfide click on the link below:
https://brainly.com/question/23293809
#SPJ4
