Frankland was convinced that an element's valence had a single value that matched with the maximum value observed. The number of valencies on atoms that are not used of what is now called p-block elements is often even. Frankland said that the unused valencies saturated each other. For example, nitrogen has a maximum valence of 5, so two valencies are left unconnected when generating ammonia; sulphur has a maximum valence of 6, so four valencies are left unattached when forming hydrogen sulphide.