Question

Arrange these ions according to ionic radius: Ca²⁺, Cl⁻, K⁺, S²⁻, P³⁻?

A) Cl⁻, P³⁻, S²⁻, K⁺, Ca²⁺
B) K⁺, Ca²⁺, Cl⁻, S²⁻, P³⁻
C) P³⁻, S²⁻, Cl⁻, K⁺, Ca²⁺
D) Ca²⁺, K⁺, Cl⁻, S²⁻, P³⁻

Answer 1

The correct order of the ions by increasing ionic radius, considering isoelectronic series and nuclear charges, is P³⁻, S²⁻, Cl⁻, K⁺, Ca²⁺, which means Option C is correct.

Step-by-step explanation:

To arrange the ions (Ca²⁺, Cl⁻, K⁺, S²⁻, P³⁻) according to increasing ionic radius, we first consider the number of electrons in each ion and their nuclear charge. Ions with the same number of electrons are part of an isoelectronic series, and the nuclear charge will affect size wherein a larger charge pulls electrons closer, resulting in a smaller ionic radius. We also consider that ions with higher negative charges generally have a larger ionic radius than those with lower negative charges, or positive charges, due to less effective nuclear charge per electron.

Given these principles:

Cations with larger charges are smaller than those with smaller charges.

Within the same charge state, cations increase in size down a group.

Anions increase in radius as the negative charge increases.

So, by applying these principles, the correct option is C) P³⁻, S²⁻, Cl⁻, K⁺, Ca²⁺. This order starts with the largest, the P³⁻ (with the smallest nuclear charge relative to its number of electrons), and ends with the smallest, the Ca²⁺ (with a larger nuclear charge and fewer electrons).