Size of Atom and Strength of Attractive/Intermolecular Forces

[Jasmine Reddy DIS 1E]

Why does a larger atom have stronger intermolecular forces?
Also, when we refer to the size of an atom, are we referring to its molecular mass, atomic number, or atomic radius?

[EllerySchlingmann1E]

Larger atoms have stronger intermolecular forces because they are more polarizable (their electron clouds are more easily distorted). This is because they have more electrons surrounding their nucleus and those electrons are not held as tightly by the nucleus due to large energy shells.

When we are talking about the "size" of an atom, Professor Lavelle and the TAs I think are generally referring to atomic radius.