Name: 共振｜分子和離子化合物的結構和特性｜AP化學｜可汗學院 (Resonance | Molecular and ionic compound structure and properties | AP Chemistry | Khan Academy)
Uploaded: 2021-01-14T10:43:01.000Z
Duration: 7 min 24 s
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- [Instructor] Let's see if we can draw the Lewis diagram

So a nitrate anion has one nitrogen and three oxygens,

So pause this video and see if you can draw that,

All right, well we've done this many times.

Nitrogen has one, two, three, four, five valence electrons

in its outer shell, and in that second shell,

And so if you just add up the valence electrons,

you would get five plus 18, which is 23 valence electrons.

This has a negative one charge right over here.

So it's going to have one more extra electron,

one more extra valence electron than you would expect

if these were just free atoms that were neutral.

that is not hydrogen to be the central atom.

It's to the left of oxygen in that second period.

in another color, so we can account for it better.

So so far we have accounted for two, four,

The next step is we would try to allocate

as many of these as possible to our terminal atoms,

so they already have two valence electrons hanging out.

So let's see if we can give them each another six,

And we are now left with no further valence electrons

It would be great if there was a Lewis structure

where we could have eight valence electrons

of these lone pairs from one of the oxygens

and turn that into another covalent bond.

So let me just erase this pair right over here,

We have eight valence electrons around each

we would just put that negative charge there.

but if this was the only way that nitrate existed

when we observed nitrate anions in the world,

and two longer bonds, and we would expect one

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共振｜分子和離子化合物的結構和特性｜AP化學｜可汗學院 (Resonance | Molecular and ionic compound structure and properties | AP Chemistry | Khan Academy)

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