Tungsten atomic properties

With respect to ammonia synthesis at 773 K, tungsten carbide (WC, 2m /g) also seems to behave like tungsten metal (W), although their physical properties differ considerably. 390 Pa of ammonia was produced at a contact time of 0.10 s under N2 + 3H2 = 101 kPa and at 773 K. H2S adsorption on only a fraction of the surface of WC inhibited the ammonia synthesis. This suggested that the three side planes (lOTO), (TlOO) and (OTlO) of hexagonal WC crystal exposed tungsten atoms in the uppermost layer. These faces would not hold carbon atmos strongly and the metallic face was considered to be the active sites for ammonia synthesis [129]. 

Physical Properties. Molybdenum has many unique properties, leading to its importance as a refractory metal (see Refractories). Molybdenum, atomic no. 42, is in Group 6 (VIB) of the Periodic Table between chromium and tungsten vertically and niobium and technetium horizontally. It has a silvery gray appearance. The most stable valence states are +6, +4, and 0 lower, less stable valence states are +5, +3, and +2. 

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