Despite the lack of linear scaling, there is, broadly, an increasing trend for both C* and O* energies in Figure . Metals that bind C* strongly (for example, Fe) also bind O* strongly and those that bind C* weakly (Au, Ag) also bind O* weakly. However, due to the noticeable amount of scatter, this general "rule" does not always hold. Consider the example of platinum: For a constant ∆E C , ∆E O is about 2 eV weaker than what linear scaling would predict. This weaker than expected binding affects the catalytic activity of Pt, where it is considered weak binding for oxygen based reactions but has a lot of interesting carbon chemistry. Furthermore, the noble metals (Au, Ag and Cu) appear to tail-off, having significantly weaker O* and C* chemisorption energies.