Silicon dioxide

[Primarygun]

I found that my text book's illustration of the glass atoms as silicon oxide, but it said that glass is formed by silicon dioxide.

Which is correct?

[Skye]

Both. Glass can formed from silicon dioxide. In this case it's chemical formula will be silicon dioxide. The word glass doesn't refer to a specific chemical, it refers to the material properties of a substance. You can have soda glass, pyrex, crystal glass, and others that aren't even based on silicon. These have different chemical compositions but are all glasses.

[pulkit]

Soda lime silicate glass is amongst the cheapest and common types. That is what is generally described in text books, it would have a formula of [MATH]Na_2SiO_3[/MATH]

[budullewraagh]

actually, glass with hydrofluoric acid becomes [math]SiF4[/math]

:\

[pulkit]

[MATH]Na_2SiO_3 + 6 HF \rightarrow Na_2SiF_6 + 3 H_2O [/MATH]

 

Not exactly [MATH]SiF_4[/MATH]

[budullewraagh]

that would make it anionic, no?

[pulkit]

Changed it to [MATH]SiF_4[/MATH] , wrote [MATH]SiF_6[/MATH] by mistake.

 

Whats anionic now ?

[budullewraagh]

nothing now, but the hexafluoride would carry a -2 charge

[Primarygun]

Does SiF4 resist corrosion from hydrofluoric acid?

[pulkit]

[MATH]SiF_4[/MATH] is the corrosion product itself. Once it has been formed, your glass has already melted away. It does not form a protective layer like aluminium oxide would over aluminium, and will not prevent further corrosion.

[wolfson]

Pulkit that was so wrong it's not even funny:

 

Na2SiO3 + 8 HF --> H2SiF6 + 2 NaF + 3 H2O

[budullewraagh]

Does SiF4 resist corrosion from hydrofluoric acid?

yes

[pulkit]

and exactly how does SiF4 prevent that ?

As mentioned H2SiF6 is formed as SiF4 disolves.

[budullewraagh]

it's already as fluorinated as it can be... although i suppose a bit of it would make hexafluorosilicic acid. sorry; forgot about that

[Gilded]

So if an atom has four outer orbit electrons, it can have them all shared with for example four fluorine atoms? This stuff is taught in Finland like in the second year of high school or something.

[budullewraagh]

heh, "shared". the fluorine really "steals" the electrons more than it "shares" them.

 

yes, 4 bonds are made by silicon in just about every silicon compound

[Gilded]

Thanks. Aren't there also double (or more) electron bonds? Like a carbon atom forming double bonds with two oxygen atoms making carbon dioxide? Or am I way off here? :<

[budullewraagh]

of course. in fact, silicon COULD form a triple bond

[pulkit]

SiC

Silicon carbide they share 4 electrons each.

One of the hardest substances known to man, hardness close to that of diamonds.

[budullewraagh]

figures. i'd like to see somebody make a lead silicide

[Gilded]

So in SiC the silicon and carbon atom share all their electrons? If so, it seems that SiC is a compound for communists.

[budullewraagh]

sorta, except the electrons are closer to the carbon than the silicon

[pulkit]

Its a very interesting compound. One of the few in which the elements belong to the same group of the periodic table (These sort ofcompounds are always interesting -- inter halogen compounds par exemple) . SiC has both structural and physical similarities to diamonds. Its crystal structure is 3-d with both Si and C involved in a complex 3-d matrice, like diamond. It is used extensively in making tools because of its hardness. It has interesting properties also becaues of its part organic nature - which is why it dissolves in organic reagents like carbon tetra chloride.

[Primarygun]

Can I made a conclusion of all fluoride compound resist corrosion form HF?

[pulkit]

Can I made a conclusion of all fluoride compound resist corrosion form HF?

 

Ceratainly not. I would imagine all sorts of reactions take place between the flourides of sulphur and HF. Or for that matter the flourides of xenon.