Question

Arrange the isoelectronic ions - Cl⁻, ca2 , k , s2- - in order of increasing radius?

1) Cl⁻, ca2, k, s2-
2) Cl⁻, s2-, k, ca2
3) s2-, Cl⁻, k, ca2
4) ca2, k, Cl⁻, s2-

Answer 1

The isoelectronic ions in order of increasing radius are: Ca²⁺, K⁺, Cl⁻, S²⁻. This order is determined by the nuclear charge, which is informed by the atomic numbers of the parent atoms from which these ions are formed.

Step-by-step explanation:

To arrange the isoelectronic ions Cl⁻, Ca²⁺, K⁺, S²⁻ in order of increasing radius, we need to consider the atomic numbers of the atoms from which these ions are derived. These ions all have the same number of electrons due to their isoelectronic nature, which is having the same electron configuration as Argon (Ar).

The ion with the lowest atomic number will have the lowest nuclear charge and thus the largest radius, while the ion with the highest atomic number will have the greatest nuclear charge, pulling the electrons closer to the nucleus and resulting in the smallest radius.

The correct order from the smallest to the largest radius is:

1. Ca²⁺ (Atomic number Z=20)
2. K⁺ (Z=19)
3. Cl⁻ (Z=17)
4. S²⁻ (Z=16)

This is because as the nuclear charge decreases, the ability of the nucleus to hold the electrons close reduces, causing the radius to increase.