Lewis Structure for N2O

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Lewis Structure for N2O

Postby TarynD_1I » Sun Nov 03, 2019 1:44 pm

Can someone please help walk me through how to draw the lowest energy Lewis Structure for N2O with N as the central atom? (12c on the dino nuggets midterm practice). I was a little confused when they explained it in the review session. Thanks!

Ariana Iranmahboub1G
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Re: Lewis Structure for N2O

Postby Ariana Iranmahboub1G » Sun Nov 03, 2019 2:20 pm

Fist you'll want to count the total number of valence electrons for N20. For N20, there will be 16 valence electrons (2*5 + 6). Then, I would draw a lewis structure that fulfills the octet rule. Then you calculate the formal charges. With simply single bonds, you'll find that the formal charge of the N atoms and O atoms are not close to zero which makes the structure not stable. That's when you'll change the structure by adding double bonds and triple bonds. Keep note that O and N are not part of the exceptions that can have incomplete or expanded octets. As you rearrange the structure, you should continue calculating the formal charge until you get to a structure that has formal charges closest to zero. Since N20 is not an ion it should have a net charge of zero. In N20, you can rearrange the structure for one N to have FC = -1, the other N to have FC=+1, and the O have FC=0. However because oxygen is more electronegative than nitrogen, rearrange the structure again so O has the FC= -1 one of the N to have FC= +1.

Frederick Keith_4C
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Re: Lewis Structure for N2O

Postby Frederick Keith_4C » Sun Nov 03, 2019 2:21 pm

N2O has 16 total valence electrons across all its atoms. And we can draw it three different ways.
1) N=N=0
(left N has 2 lone pairs (4 e-) and right O has 2 lone pairs (4 e-))
2) N-N(triple bond)O
(left N has 3 lone pairs (6 e-) and right O has 1 lone pair (2 e-))
3) N(triple bond)N-O
(left N has 1 lone pair (2e-) and right O has 3 lone pairs (6e-))
All of the structures use the 16 valence electrons, so in order in to figure out which is the most stable structure, we have to look at the formal charge.
In the first structure, the first N has a charge of -1, the second N a charge of +1, and O has 0.
In the second structure, the first N has a charge of -2, the second N a charge of +1, and O has +1.
In the third structure, the first N has a charge of 0, the second N a charge of +1, and O has -1.
We can yeet the second structure because of that -2 charge, so now we're looking at 1 and 3. But they be looking kinda identical lowkey. So to figure out which one is the most stable, we want to choose the structure with a negative formal charge on the most electronegative element.
Because structure 3 has a -1 charge on its O, which is more electronegative than N, then we can say that structure 3 makes the best Lewis Structure.

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