The reverse of adsorption is desorption, the adsorbate splitting from adsorbent. The bond between the adsorbate and adsorbent in chemisorption is either ionic or covalent. In chemisorption, the adsorbate and adsorbent share electrons signifying the formation of chemical bonds. Experimentally, there is clear evidence for adsorbate/adsorbate interactions in heat of adsorption data. This process creates a film of the "adsorbate" on the surface of the "adsorbent". The exact kinetics of SAM formation depends on the adsorbate, solvent and substrate properties. Nitrogen is the most commonly employed gaseous adsorbate used for surface probing by BET methods. Diffusion of the adsorbate is thus an important factor. This section provides a kinetic derivation for a single adsorbate case. The first stage is for the adsorbate particle to come into contact with the surface. There are two kinds of adsorbate/adsorbate interactions&colon; direct interaction and indirect interaction. The model also ignores adsorbate/adsorbate interactions. The binding energy varies with the combination of the adsorbate and surface.