Which of the following is expected to have the smallest radius?1 pointP3-S2-Cl-Ca2+K+

The size of an atom or ion is determined by its atomic radius. The atomic radius tends to decrease across a period from left to right and increase down a group.

1. P3-: Phosphorus (P) is in the 3rd period of the periodic table. The P3- ion has gained three extra electrons, making it larger than a neutral P atom.

2. S2-: Sulfur (S) is also in the 3rd period, but to the right of P. The S2- ion has gained two extra electrons, making it larger than a neutral S atom, but smaller than P3- because it is further to the right in the period.

3. Cl-: Chlorine (Cl) is in the same period but even further to the right. The Cl- ion has gained one extra electron, making it larger than a neutral Cl atom, but smaller than S2-.

4. Ca2+: Calcium (Ca) is in the 4th period, so a neutral Ca atom would be larger than any atom in the 3rd period. However, the Ca2+ ion has lost two electrons, making it smaller than a neutral Ca atom.

5. K+: Potassium (K) is also in the 4th period, but to the left of Ca. The K+ ion has lost one electron, making it smaller than a neutral K atom, but larger than Ca2+ because it is further to the left in the period.

So, the ion expected to have the smallest radius is Ca2+.