Question

why the size of radius is smaller than its parents atom ​

Answer 1

Cations are always smaller than their parent atoms this is because they have lesser electrons, while their nuclear charge remains the same. The remaining electrons are, therefore held more tightly by the protons in the nucleus and thus their radii.are smaller than the parent atoms. This is opposite in case of anions.

Answer 2

I know that atomic radii decreases from left to right across a period as the effective atomic number increases, and they increase down a group as successive shells are occupied.

Also that cations are smaller than their parent atoms and anions larger.

However, when comparing for example, Cs+1 and Ba, Cesium would originally be larger, but since it is in its cation form, does it decrease in size so much that it is smaller than the Barium?

Cs +1 and Ba have the same number of electrons, but Cs has more protons. Therefore, the proton-electron attraction is much greater than in Ba, making it smaller.

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