Question

The following ions all have the same number of electrons. Order them according to their expected size.

A. Cl⁻ > S²⁻ > P³⁻
B. P³⁻ > S²⁻ > Cl⁻
C. S²⁻ > P³⁻ > Cl⁻
D. Cl⁻ > P³⁻ > S²⁻

Answer 1

Atoms and ions that have the same electron configuration are isoelectronic and their size depends on the nuclear charge. The correct order for the given ions is Cl⁻ > S²⁻ > P³⁻.

Step-by-step explanation:

Atoms and ions that have the same electron configuration are said to be isoelectronic. For atoms or ions that are isoelectronic, the number of protons determines the size. The greater the nuclear charge, the smaller the radius in a series of isoelectronic ions and atoms. In this case, the ions are Cl⁻, S²⁻, and P³⁻. Since Cl⁻ has the greatest nuclear charge, it will have the smallest radius. On the other hand, P³⁻ will have the largest radius as it has the smallest nuclear charge. So the correct order would be: Cl⁻ > S²⁻ > P³⁻.