Definitions and Connections between Polarisability and Polarizing Power

[Sheik Sahadat]

Hello,
Would someone please be able to explain to me what exactly polarizability and polarizing power are? And what is their relation to the other periodic trends? As of right now, I just know that polarizing power has the same trend as electronegativity and polarizability has the same trend as atomic radius.
Thank you

[Ishita S 2E]

Polarizability is essentially how easily an electron cloud is distorted by an electric field. This tends to increase as the number of electrons in an atom increases and also increases from right to left with atomic radii. On the other hand, polarizing power is the ability of a cation to distort the electron density of an anion. Cations that are smaller and more positively charged have greater polarizing power, and when you go down a periodic group, then polarizing power decreases because the atom becomes larger.

[Lan Wei 3I]

To add on, large ANIONS have high polarizability (because the nucleus has weak control over its outermost electrons) while small, highly charged CATIONS have high polarizing power. Compounds consisting of small, highly charged cations and large, polarizable anions form bonds with a lot of covalent characters.