Question

Which of the following ranks these isoelectronic species in order of increasing atomic radii?

A) Cl-, S₂-, P₃-
B) P3-, S₂-, Cl-
C) S2-, P₃-, Cl-
D) Cl-, P₃-, S₂-

Answer 1

The order of increasing atomic radii for the isoelectronic species is in option C) S2-, P₃-, Cl-.

Step-by-step explanation:

We see that S and Cl are at the right of the third row, while K and Se are at the far left and right ends of the fourth row, respectively. K+, Cl-, and S2- form an isoelectronic series with the [Ar] closed-shell electron configuration; that is, all three ions contain 18 electrons but have different nuclear charges. Because K* has the greatest nuclear charge (Z = 19), its radius is smallest, and S2- with Z = 16 has the largest radius. Because selenium is directly below sulfur, we expect the Se2- ion to be even larger than S2-.

The atomic radius is defined as the distance from the nucleus of an atom to the outermost shell of its electrons. It is typically measured in picometers (pm), which are equal to 10^-12 meters.