Less cohesive or chemical attraction between surface atoms or molecules.

Energy transferred to a surface atom can be held long enough for more and more energy to build up.

The response of these surface atoms would be to attempt to reduce their interatomic distance in order to increase surrounding charge density.

Therefore, surface atoms would create a positive surface stress (tensile).

The molecule may also react with surface atoms to change its chemical properties.

The reactivity of heterogeneous catalysts occurs at the surface atoms.

This leaves the surface atoms without a neighboring atom on one side, which inherently alters the electron distribution.

This state of higher energy is unfavorable, and the surface atoms will try to reduce it by binding to available reactive molecules.

This is often accomplished by protein adsorption, where the surface atoms are reduced to a more advantageous energy state.

The energy required to remove an atom from the surface depends on the number of bonds to other surface atoms which must be broken.