CHEMISTRY COMMUNITY

How can you tell whether one element is more polarizable than another? Also, is there a difference between an element that has more polarizing power vs. an element that is the most polarizable?

An atom is polarizable if it has a larger radius and less electronegativity.

Polarizing power is the ability of a cation to distort an anion by pulling electrons away from the anion. Polarizability is the ability to pull those electrons toward the anion.

The larger the radius of the atom, the more easily an atom can be polarized because the electron clouds are further from the nucleus and can distort more easily. The polarizability will decrease across a period because the increasing Z eff that is pulling the electrons closer to the nucleus.

Polarizing power is related to cations and their ability to attract the valence electron shell from a nearby anion. The tendency for an anion to become polarized by a cation or how easily its electron cloud is distorted is known as polarizability.
Smaller, more positive cations can pull electrons more strongly and thus have more polarizing power.
Larger anions with smaller negative charges are more easily polarizable .

An atom has high polarizing power if they are likely to cause the electron distortion of another atom. And these are usually small, highly-charged cations (so elements in the upper left of the periodic table).
An atom is highly polarizable if they are likely to have their electron distorted. These atoms are usually anions with a large radius and high electronegativity (so elements in the lower right of the periodic table).

Thus, the polarizing power atom causes the polarizable atom to have an electron distortion. Think of this as cause-and-effect.