Theoretical Studies of Chemisorbed Hydrogen on Metals

Theoretical Studies of Chemisorbed Hydrogen on Metals 1. Time of Adsorption 

It seems likely that other physical data, such as contact potentials, will be required to decide the mode of adsorption in cases like ethylene. As we shall see, data on the catalyzed exchange reactions of ethylene are most easily interpreted on the basis of two-point adsorption at the double bond. This is indeed what we should expect from the reactive character of the mobile t electrons. 

A paper by 0. Beeck (33d) has only recently come to the author s notice. Working with evaporated films of metal of area of the order of 10,000 cm. Beeck has confirmed all Roberts results on the speed, extent, and heat of adsorption as a function of surface covered, for the adsorption of hydrogen on tungsten. Nickel shows a similar behavior. This makes extremely likely the view that adsorption on tungsten powder is complicated in some fashion, if not by solution, as suggested above, then by some kind of physical or chemical heterogeneity of the surface, as in the Halsey and Taylor picture. 

If 6 be the fraction of occupied sites, assumption (a) leads to the linear relationship found in Fig. 4. 

On assumption (b), however, up to fl = 0.5, the atoms may arrange themselves so that no two atoms are nearest neighbors. This may be seen by reference to Fig. 7. 

---