2D.11

[Seungri_Han_2J]

Arrange the anions Cl-, Br-, N3-, O2- in order of increasing polarizability and give reasons for your decisions.

I know that polarizability increases when the size of ions increases. So, I get that N3- has a greater polarizability than o2- because o2- has a greater number of protons, meaning it has a greater effective nuclear charge, pulling electrons closer to the nucleus. However, I don't get why polarizability of Cl- is greater than that of both N3- and O2- and why Br- has the greatest polarizability. I thought Cl- and Br- would be less than O2- since they have a greater number of protons and therefore effective nuclear charge. Why is my reasoning wrong?

[Bilan Guan 2H]

Yes, polarizability is how easily an electron cloud can be distorted, so as the atom size increases the polarizability increases. Br- has the greatest number of electrons followed by Cl-, with the same reasoning you mentioned for N3- and O2-, Br- and Cl- are both larger atomic radius making its electron cloud more easily distorted since those electrons are farther away from the nucleus compared to N3- and O2- which is a smaller ion