Transition Elements: Octet Rule, Lewis Dot Diagrams, Stability

[scott_alexsk]

I have already talked about this a little, but I have some more questions. Do transition elements obey the Octet rule? Also can you draw lious dot diagrams for them. It does not seem like you can, but I would like to know why. Also is Manganese the most stable transition element along with others in its column?
Thanks,
Scott

 

[Unco]

G'day, Scott.

Metals don't form covalent bonds so lewis diagrams do not apply to them.

That said, transition metals do form dative covalent bonds in complexes. In this case, the octet rule doesn't apply because d orbitals are being used to bond (the octet rule basically means getting full outer s and d subshells), and size of ligands and energy released are the kinds of factors that determine how many ligands bond to the transition metal ion.

 

[movies]

Metals can form covalent bonds! The definition of covalency is a little lacking, since it is based on electronegativity differences, but you can definitely have convalent bonds with metals. There are lots of compounds that have metal-metal bonds which must be covalent.

You could draw a Lewis dot structure for a metal, but it's more complicated because many transition metals don't obey the octet rule directly. The most common "rule" for transition metals is the 18 electron rule, which states that when you count up all the electrons donated to the metal center you would ideally have 18 electrons. The way that you count different ligands can be a little complicated, and there are plenty of perfectly stable transition metal complexes that don't have 18 electrons.

 

[scott_alexsk]

I was told that the half shell for transition elements is the most stable 'place.' Is my understanding correct? Also what is the maxium number of bonds a transition metal can form in a chemical reaction?
Thanks,
-Scott

 

[movies]

Both the half-filled and filled subshell configurations are reasonably stable for transition metals.

The number of ligands to a metal depends on the number of electrons, the oxidation state of the metal, the size of the metal atom, etc. Common coordination numbers are 4 and 6, but there are plenty of compounds with 2 or 3 as well.