June 19, 2019, 09:15:14 AM
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Topic: Is quartz a silica atom bound to three or four oxygen atoms:  (Read 208 times)

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Offline galpinj

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Hey everyone,

I was reading about quartz and how it is a crystalline structure based off a tetrahedron (silicon in the center and 4 oxygen molecules around it). However, all the images (including those from Wikipedia and UNSW Sydney) show quartz as a silica atom attached to only three oxygen atoms. This type of image is also rampant when I do a google search, so I have to ask: "is quartz (and glass) a silica atom bound to three or four oxygen atoms"? If it is bound to four, why are they only showing three bonds in the images?

I attached a couple images for the group to see what I mean

Offline Borek

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Re: Is quartz a silica atom bound to three or four oxygen atoms:
« Reply #1 on: June 12, 2019, 02:56:53 AM »
These are poorly drawn, flat 2D representations of a 3D structure, kind of a flattened cross section. As you wrote, Si atom sits in the center of a tetrahedron with four oxygen atoms (not molecules!) occupying all four vertices.

Sadly, it is quite difficult to represent this structure in a clear, unambiguous way on a paper.
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Offline AWK

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Re: Is quartz a silica atom bound to three or four oxygen atoms:
« Reply #2 on: June 12, 2019, 03:04:09 AM »
These are projection drawings and for the inexperienced chemist they have the value of "nice patterns". You can take a look yourself and make real drawings of quartz and thousands of other organic and inorganic compounds using Mercury and CIF files
https://www.ccdc.cam.ac.uk/support-and-resources/Downloads/
http://rruff.geo.arizona.edu/AMS/minerals/Quartz
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Offline AWK

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Re: Is quartz a silica atom bound to three or four oxygen atoms:
« Reply #3 on: June 12, 2019, 06:06:39 AM »
different projection of the same quartz. The tetrahedral arrangement of silicon can be presented
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Offline galpinj

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Re: Is quartz a silica atom bound to three or four oxygen atoms:
« Reply #4 on: June 12, 2019, 11:12:11 AM »
Wow, thank you, everyone! This completely resolves my question, and I will definitely take a look at the website that was linked.

Offline David Tan

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Re: Is quartz a silica atom bound to three or four oxygen atoms:
« Reply #5 on: June 14, 2019, 04:17:31 PM »
Si is connected to 4 oxygen atoms if you look at its 3D structure. Tetrahedral shape with respect to the Si atoms.
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