In a compound like Molybdenum disulfide (MoS2), what is going on with the electrons? I came across this in the context of redox reactions where the sulfurs get -2 giving the Mo +4. Oxidation numbers are the theoretical charges if the electrons in the bonds were possessed completely by the more electronegative element. Does this mean the Mo has a double bond to each S? How is this possible when Mo only has 1 valence electron?

Question

In a compound like Molybdenum disulfide (MoS2), what is going on with the electrons? I came across this in the context of redox reactions where the sulfurs get -2 giving the Mo +4. Oxidation numbers are the theoretical charges if the electrons in the bonds were possessed completely by the more electronegative element. Does this mean the Mo has a double bond to each S?  How is this possible when Mo only has 1 valence electron?

abb0t · Answer

Well, Mo has more than one electron. Remember that Mo also has it's d-electrons available which are able to form bonds with other MoS2 molecules. Are you familiar with Molecular Orbital? I think I can use that to explain this a bit better. 

Since the preferred state of Mo is +4, therefore, you would need a relatively soft base, such as the one you have there, S2- to stabilize it.

abb0t · Answer

Also, I don't think valence electrons counts for transition metals. You must use $$d^n$$ electron count to figure this out.

anonymous · Answer

Thanks abbot