Lewis structures

[italian831]

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Yes, this may seem like a dumb question, but can someone explain lewis structures to me? For example, If oxygen has 6 valence electrons, why do you draw it with eight? haha sorry for the dumb question!

thanks!

 

[mj1878]

Here's some exceptions to the octet rule, which I'm sure is what's confusing you. Try to get out of the mindset that every atom HAS to have 8 electrons. Actually, the octet rule isn't much of a rule, because there are so many exceptions to it. If you make sure that the oxidation states are correct for the atoms in the molecule and the molecule itself, then you're okay.

 

[R.P. McMurphy]

Yes, this may seem like a dumb question, but can someone explain lewis structures to me? For example, If oxygen has 6 valence electrons, why do you draw it with eight? haha sorry for the dumb question!

thanks!

every atom wants to have 8 electrons......thats why oxygen has a charge of -2 (6 electrons.....and wants two more, giving it -2)

 

[mj1878]

every atom wants to have 8 electrons......thats why oxygen has a charge of -2 (6 electrons.....and wants two more, giving it -2)

Actually, molecular oxygen O2 does NOT have a charge. That's why it's O2, and not O2 2-.

 

[R.P. McMurphy]

Actually, molecular oxygen O2 does NOT have a charge. That's why it's O2, and not O2 2-.

lol i wasn't talking about molecular oxygen.....but you obviously know your diatomic molecules!!!

 

[Julius Erving]

Yes, this may seem like a dumb question, but can someone explain lewis structures to me? For example, If oxygen has 6 valence electrons, why do you draw it with eight? haha sorry for the dumb question!

thanks!

when you have a covalent bond, the octet rule is normally enforced. So Oxygen bound to 2 hydrogens will have 8 electrons around it. Two of those electrons technically belong to the hydrogens (one from each), but are placed around the oxygen as if the oxygen has 8 electrons instead of six.

 

[xanthomondo]

lol i wasn't talking about molecular oxygen.....but you obviously know your diatomic molecules!!!

Ouch lol

Note though, that lewis dot theory fails to explain O2...you need molecular orbital theory to do it

Its actually a radical

 

[EddieIndy]

Ouch lol

Note though, that lewis dot theory fails to explain O2...you need molecular orbital theory to do it

Its actually a radical

How come?

 

[alpinesunrise]

As others have mentioned, Oxygen doesn't HAVE to have eight electrons, it just wants to. This applies to pretty much any other element you'll run across in gen chem or orgo, the main exception being Hydrogen (which has one and wants to have two). Oxygen is six elements from the left of the periodic table, so it has six valence electrons. In general, when you see oxygen in an uncharged lewis structure with eight electrons, remember that oxygen "owns" only six of those. The other two come from covalent bonds. For example, in water, the hydrogens supply one additional electrons each, for a total of eight elecrons. In an alcohol, carbon and hydrogen each supply an additional electron, again for a total of eight.

Hopefully this helps.

 

[xanthomondo]

How come?

If you look at the molecular orbital diagram (let me do searchhh....)

theres two unpaired bad boys in there...

Reference:
http://www.meta-synthesis.com/webbook/39_diatomics/diatomics.html

 

[EddieIndy]

If you look at the molecular orbital diagram (let me do searchhh....)

theres two unpaired bad boys in there...

Reference:
http://www.meta-synthesis.com/webbook/39_diatomics/diatomics.html

Yep, you're right, it IS a radical... never thought of it this way...

 

[xanthomondo]

Yep, you're right, it IS a radical... never thought of it this way...

its lewis symbol is so pretty and perfect too 🙁 ....but that theory has a lot of failings...hence the whole "resonance" add on