Atomic radii of cations

[205743684]

Question: Arrange The Following Species By Decreasing Atomic Radii. S2-, P3-, CI-, Ca2+, K+

I know atomic radius increases down the group and decreases across the period but how do ions affect this? Also how would we know if the atomic radius is smaller if they are in different groups And in different periods

[Jiayi_Cao_3E]

Hi!

All of these ions have the exact same number of electrons (not valence but overall #). The difference between them is the number of protons in their nucleus. The more proton an ion has in this case, the more closely the electrons will be held to the nucleus due to larger nuclear attraction. Therefore, Ca2+ actually has the smallest radius since it has the most protons.

The increase in atomic radius down a group is much more significant than a decrease across a period because going down a group adds an entirely new energy level and subshell to the atom/ion, rather than simply adding a proton and an electron across a period.

[Claudia Longo 2J]

Question: Arrange The Following Species By Decreasing Atomic Radii. S2-, P3-, CI-, Ca2+, K+

I know atomic radius increases down the group and decreases across the period but how do ions affect this? Also how would we know if the atomic radius is smaller if they are in different groups And in different periods

Ions affect this in the way that ions account for differences between atomic radii- anions have larger atomic radii than cations and the stronger the negative charge, the larger the atomic radius for that ion. Keep in mind that the atomic radius increases down a group and across the period (to the left).

[Kavya Anand 2B]

In this example, though all the ions have the have number of electrons, the ions with the higher number of protons will have the smaller atomic radius because the electrons are pulled closer due to the higher positive charge in the nuclei.