[peterpan1372]

Which one of the following covalent substances could exist as a giant structure?
A  SiCl4
B  SiO2
C  ICl
D  Cl2O
E  H2S
F  CF4

I seriously don't know which one to choose...  I know that giant structures have very high melting points and variable conductivity, but do not know why/or why not everyone of them could be right or wrong..
Appreciating any *delete me*

[Arkcon]

Now this is a tough one.  What would you consider a giant structure?  What wouldn't a giant structure be made of?  Ever see a a liquid or gas be a structure?

[peterpan1372]

What would you consider a giant structure?  What wouldn't a giant structure be made of?  Ever see a a liquid or gas be a structure?

to first question: I already stated.
to second and third: I dont know which one of them could be gases or liquids...

[wildfyr]

This question makes almost no sense. I think I know what they are getting at, and what the answer probably is, but the concept is so ridiculous I feel silly even trying.

[peterpan1372]

and what is the concept?

[billnotgatez]

Does the BMAT actually use these words

giant structure

[wildfyr]

I think they mean a polymeric structure

[wildfyr]

Here, lets go through the posibilities in terms of the bonds they make.

A  SiCl4
B  SiO2
C  ICl
D  Cl2O
E  H2S
F  CF4

Only one of these is not "happy" existing as a molecule, so it is likely only a repeat unit in a larger structure. Can you identify which one of these stands out in that regard? Think about the number of bonds each atom likes to have.

[peterpan1372]

what do you mean?

what does Cl2O , for example, like?

[wildfyr]

Have you learned about oxidation numbers?

[peterpan1372]

Cl->-1 and O ->-2

[wildfyr]

Well yes, ok. Though that is in fact the funkiest example, since Cl is actually in the +1 oxidation state for that compound. Don't ask why its not O +2 Cl -1, it has to do with ionization energies I think.

Aside from that, all those compounds are generally in their normal oxidation states. Do you see one that if you drew the bonding out, would be very amenable to making bonds with other versions of itself?

[peterpan1372]

I would say SIO2... reason: since SI has a charge of +4 and O -2, that wouldn't equal it out... right?

[wildfyr]

Correct. And the term we are really dealing with, as opposed to 'Giant structure" is "network covalent bonding." I had never heard this term "giant structure" before, and googling it leads to rather less technical sites than I would usually prefer to use. It really threw me off.

https://en.wikipedia.org/wiki/Network_covalent_bonding

Also, for petes sake, its Si for silicon, not SI.

[peterpan1372]

yeah, but why B)? why do pairs which don't equal them out exist as a "giant structure?"