username3875292
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Why is the bond angle of SO2 120 degrees?

It's linear so it should be 180?

Thanks a lot in advance
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Sara Yasin
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Hope that make sense
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charco
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(Original post by chem11)
Why is the bond angle of SO2 120 degrees?

It's linear so it should be 180?

Thanks a lot in advance
It's not linear. Do a TSR search to find many threads all about this.
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Katarinanokat
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This is a really easy mistake to make! However, it's good to remember that Silicon, although in the same group as carbon, does not form stable double bonds. This is due to poor orbital overlap (there's a great video on why silicon can't form a double bond on khan academy) and as a result it would not form a stable linear structure with oxygen.

Silicon dioxide is a giant molecular structure where each oxygen is bonded to 2 silicons, but each silicon is bonded to 4 oxygens. It's confusing, but it's one of those rules you should remember.

As a result silicon dioxide is giant covalent molecule and has a high melting point.

However, I do think you're wrong about the 120 degree bond angle. Silicon is bonded to 4 oxygens, meaning it should exhibit a tetrahedral structure and thus have 109.5 degrees between each bond.

Are you sure it says 120?
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maths_2001
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(Original post by Katarinanokat)
This is a really easy mistake to make! However, it's good to remember that Silicon, although in the same group as carbon, does not form stable double bonds. This is due to poor orbital overlap (there's a great video on why silicon can't form a double bond on khan academy) and as a result it would not form a stable linear structure with oxygen.

Silicon dioxide is a giant molecular structure where each oxygen is bonded to 2 silicons, but each silicon is bonded to 4 oxygens. It's confusing, but it's one of those rules you should remember.

As a result silicon dioxide is giant covalent molecule and has a high melting point.

However, I do think you're wrong about the 120 degree bond angle. Silicon is bonded to 4 oxygens, meaning it should exhibit a tetrahedral structure and thus have 109.5 degrees between each bond.

Are you sure it says 120?

Is SO2 not referring to Sulfur Dioxide rather than anything involving Silicon?
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Katarinanokat
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(Original post by maths_2001)
Is SO2 not referring to Sulfur Dioxide rather than anything involving Silicon?
You're right. Sincere apologies, I was writing about silicon dioxide. Sorry for confusing you.

Your book is right, silicon dioxide is 120 degrees (actually <120 to be strictly true, but that's a different story)

Sulfur has 6 electrons in its valence shell, 4 of which are used to bond with oxygen (as the bonds are double).

That leaves 1 lone pair of electrons. Bonding angles depend on electron domains, which include bonding pairs and lone pairs. A double bond is one electron domain, and as there are 2 oxygens there are 2 bonding electron domains. However, the lone pair cannot be ignored, it becomes the third electron domain.

Therefore, sulfur dioxide has 3 electron domains (AB2E1 is how it's described, where A is the silicon, B are the oxygens, and E is the lone pair)

Therefore, it is trigonal planar with 120 degrees between the bonds. Although, lone pairs tend to repell more than bonding pairs, so it's slightly smaller than 120 (I think around 119 after a quick google search?)

Is that better? Sorry for the confusion I should really read closer!
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username3875292
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(Original post by charco)
It's not linear. Do a TSR search to find many threads all about this.
Are double bonds are treated the same as single bonds?
I still don't get it
I do know that 2 bond pairs and 1 lone pair is 120 but don't understand why..

To calculate electron pair for SO2 I know S has 6 electrons so it's 6 + 4=10/2 = 5 pairs of electrons?
it's a double bond so two electrons from each oxygen giving 4 electrons in total?
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Sara Yasin
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Double bonds are treated like single bonds
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