Bond Strength vs Intermolecular Strength

[fionaxie_1d]

Hi there,

I am wondering why bond strength is weaker when atoms are larger, but london dispersion forces are stronger when atoms are larger. Can someone explain this relationship and the reason why this is?

[leafypsycho]

Hi Fiona,
When determining the relationship between bond strength and atomic size, we need to consider how tightly the atom holds onto electrons. When an atom's size is larger, the valence electrons are further from the nucleus. Since the distance is so far, this results in a weaker attraction and weaker bond.
On the other hand, when determining the relationship between London Dispersion Forces and atomic size, we need to cons=sider how polarizable an atom is. Larger atoms have more electrons and are more polarizable (electrons can be easily moved around). If an atom is more polarizable, it is easier for atoms to create temporary dipoles, which leads to stronger LDFs.
Hope this helps!