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Topic: Giant Structure  (Read 14829 times)

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Offline peterpan1372

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Re: Giant Structure
« Reply #30 on: September 19, 2017, 02:22:09 PM »
which book(s) would you recommend?

Offline wildfyr

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Offline peterpan1372

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Re: Giant Structure
« Reply #32 on: September 19, 2017, 02:31:18 PM »
but still I want to know the answer why SiO2 is a giant molecule and the rest not...

Offline wildfyr

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Re: Giant Structure
« Reply #33 on: September 19, 2017, 02:40:28 PM »
Corribus has already given an extremely precise correct answer

Quote
Oxygen likes to form two bonds, and silicon, like carbon, likes to form four. However unlike carbon, silicon does not like to form double bonds because it is a bigger atom and the p orbitals responsible for forming pi bonds are more diffuse, and so overlap between p orbitals on adjacent nuclei is poor. For this reason, CO2 is a small molecular gas with formula O=C=O, whereas silica, which has the same type of (SiO2) forms an extended structure characterized by single bonds between silicon and oxygen atoms. It is the only structure available that minimizes the number of pi bonds formed with silicon atoms.

Offline peterpan1372

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Re: Giant Structure
« Reply #34 on: September 19, 2017, 02:46:52 PM »
So, why did you brought up the oxidation number when it has nothing to do with the question @wildfyr ?

Offline wildfyr

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Re: Giant Structure
« Reply #35 on: September 19, 2017, 03:05:13 PM »
To help you see the point about how many bonds a given materials "likes" to make, as Corribus pointed out in his first sentence.

Offline peterpan1372

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Re: Giant Structure
« Reply #36 on: September 19, 2017, 03:08:00 PM »
is there also another way to know whether a molecule like to form sigma or pi bonds without pre-knowledge?

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Re: Giant Structure
« Reply #37 on: September 19, 2017, 03:15:47 PM »
is there also another way to know whether a molecule like to form sigma or pi bonds without pre-knowledge?

Yes, it is based on basic concepts of quantum chemistry, as it depends on which atomic orbitals are involved in the bond. No, I won't get into details, as it is part of the basic chemistry course we told you to follow.
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Offline peterpan1372

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Re: Giant Structure
« Reply #38 on: September 19, 2017, 04:25:13 PM »
As I understood it: Silicon has a electronic configuration of 1s^2 2s^2 2p^6 3s^2 3p^2
in contrast, carbon has 1s^2 2s^2 2p^8 ... based on that, Si is more inclined to build sigma bonds because it has more s orbitals filled than p orbitals, or?

Offline peterpan1372

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Re: Giant Structure
« Reply #39 on: September 19, 2017, 04:26:53 PM »
if that is right, why is SiO2 the right answer and not SiCl4 ? because of the fact that all electrons are "used up" at SiCl4? (Hence, it would have space free to "stretch" itself like in Si02 ?)

Offline Corribus

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Re: Giant Structure
« Reply #40 on: September 19, 2017, 05:20:13 PM »
Because unlike oxygen, which tends to bond twice, chlorine tends to bond only one time. The reason for these numbers of bonds is related to the respective # of valence electrons in each atom and the "desire" of the atom to have eight (or two, in the case of first row) electrons in the valence shell - something called the octet rule. Your general chemistry text should have a lot to say about valence electrons, the octet rule, and bonding. I suggest you read these chapters carefully - learning these concepts is enough to understand fully how to answer this question, and, frankly, a lot of general chemistry. If you don't have a general chemistry book you can find plenty of helpful videos online - e.g., https://www.youtube.com/watch?v=gsvR4AZGRSk. These are concepts too detailed and extensive to teach to you in an online forum.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline peterpan1372

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Re: Giant Structure
« Reply #41 on: September 19, 2017, 06:24:58 PM »
As I understood it: Silicon has a electronic configuration of 1s^2 2s^2 2p^6 3s^2 3p^2
in contrast, carbon has 1s^2 2s^2 2p^8 ... based on that, Si is more inclined to build sigma bonds because it has more s orbitals filled than p orbitals, or?

is that right?

Offline Corribus

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Re: Giant Structure
« Reply #42 on: September 19, 2017, 06:45:33 PM »
No.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline peterpan1372

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Re: Giant Structure
« Reply #43 on: September 19, 2017, 07:07:10 PM »
what is wrong with the explanation?

Offline Corribus

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Re: Giant Structure
« Reply #44 on: September 19, 2017, 08:02:25 PM »
Why don't you read about valence electrons in your chemistry textbook and tell us what you think is wrong with what you wrote.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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