2D. 11

[Ziyan Wang 3J]

Arrange the anions Cl-, Br-, N 3-, and O 2- in order of increasing polarizability. What's the general rule of polarizability?

[kevinchang_4I]

Arrange the anions Cl-, Br-, N 3-, and O 2- in order of increasing polarizability. What's the general rule of polarizability?

The general rule of polarizability is the larger the atom, the more polarizable. This is because the larger the atom, the less influence the positively charged nucleus has on the outer electrons, thus making it more polarizable.

O2- < N3- < Cl- < Br-

This makes sense if we follow the size rule. O2- and N3- are tricky however, as O2- at first glance would be larger than N3- so it should be more polarizable. This is not the case though, as O2- has the same # of electrons in the same shell as N3- but more protons, thus making it smaller and less polarizable.

[Eunice Nguyen 4I]

Generally, polarizability increases as the volume occupied by electrons increases. On rows of the periodic table, polarizability therefore decreases from left to right, and it increases down on columns of the periodic table. You can also divide it between anions and cations. Anions that are large are expected to be highly polarizable, while cations that are small and highly charged are expected to have high polarizing power.
The order would therefore be: O2- , N3- , Cl- , Br-