Layman question: Do those shapes of molecules in diagrams really look like that? Watch

Harambulus
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Ie. do molecules really have that shape under a microscope or is it just a 'handy way of thinking about things'?

I used to think it was just a key and not real until I was wathcing a documentary on chemistry which said the benzene molecule curls around to form the benzene ring and that is how the periodic table was completed and everything ;fit together.

As such I presumed then that they must have been referring to the real shapes of molecules.

Could someone explain how the shapes relate to one another ie those little lego diagrams how did they find out that they had those shapes?

I should get back to reading my basic chemistry book but I often get ahead of myself with questions
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alow
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Pretty much, yeah. As long as you draw all of the bond lengths and angles right it'll be fairly close.


That's a microscope image of some interlocking benzene rings from here.
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Harambulus
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Ye I just found that myself. Ok so Im reading they only just found out with todays technology that this is what they look like under a scope so how did they first find this out? because these diagrams have been in use for like 100 years havnet they? long before today's 'scopes?
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alow
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(Original post by Harambulus)
Ye I just found that myself. Ok so Im reading they only just found out with todays technology that this is what they look like under a scope so how did they first find this out? because these diagrams have been in use for like 100 years havnet they? long before today's 'scopes?
VSEPR. They used what they knew about electrostatic repulsion and atomic structure to predict what molecules should look like.
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Mockery
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Valence-Shell Electron-Pair Repulsion Theory (VSEPR)

You might find this to be an informative and interesting read



(Original post by alow)
VSEPR.
Beat me to it!
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Harambulus
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Fascinating stuff! I have alot of reading to do
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Ari Ben Canaan
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(Original post by Harambulus)
Ie. do molecules really have that shape under a microscope or is it just a 'handy way of thinking about things'?

I used to think it was just a key and not real until I was wathcing a documentary on chemistry which said the benzene molecule curls around to form the benzene ring and that is how the periodic table was completed and everything ;fit together.

As such I presumed then that they must have been referring to the real shapes of molecules.

Could someone explain how the shapes relate to one another ie those little lego diagrams how did they find out that they had those shapes?

I should get back to reading my basic chemistry book but I often get ahead of myself with questions
Although, Valence Shell Electron Pair Repulsion theory (VSEPR) does help us figure out the real 3D geometry of different molecules, it does have its failings.

A more complex and thorough analysis can be carried out using Molecular Orbital (MO) theory. You can get a qualitative udnerstanding of a lot of a molecule's reactivity and shape by simply drawing out an MO diagram. I encourage you to have a look at the MO diagram of Oxygen and Nitrogen as it will help explain why one is paramagnetic and the other diamagnetic.

If you're looking for hard numbers to attach to bond lengths, bond angles, distances etc. you'd probably apply MO theory in a computational setting.
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username913907
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(Original post by Ari Ben Canaan)
If you're looking for hard numbers to attach to bond lengths, bond angles, distances etc. you'd probably apply MO theory in a computational setting.
Well it's that or a degree in QM, a massive pad of paper, a calculator and far too much free time!
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Harambulus
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Another question which has sprung to mind is- are molecules all that a substance is made up of? So a 'substance', say a piece of steel, is 100% of its 'mass' just a huge bunch of 'steel molecules' ie a bunch of those little shapes piled on top of each other :P?

Im slowly reading through a beginners book on chem but Im still in the early stages yet.
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alow
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(Original post by Harambulus)
Another question which has sprung to mind is- are molecules all that a substance is made up of? So a 'substance', say a piece of steel, is 100% of its 'mass' just a huge bunch of 'steel molecules' ie a bunch of those little shapes piled on top of each other :P?

Im slowly reading through a beginners book on chem but Im still in the early stages yet.
Steel would usually be made up of Iron and Carbon atoms (along with some different things for different stells and impurities). But basically yes. Metals are a little different as they exhibit 'metalllic bonding' where the electrons bonding atoms together are partially delocalised (which is why they're such good electrical conductors).

The majority of the mass of any substance made of molecules actually comes from the binding energy of the quarks in neutrons and protons in the constituent atoms nuclei rather than directly from the mass of the quarks themselves. (plus a little -although less- from the binding energy of the molecules in the substance).
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Kate Ricketts
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I like this Molecule editor for iPad "3D Molecules Edit & Test"

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