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Covalent bonding in NH2- and molecular geometry

I really don't understand how NH2- is negatively charged.
As far as I understand, the molecule has one lone pair, one covalently bonded pair, and one dative bond, which I am sure would make the molecule positively charged.

Also, what would the angle be?

Any help would be much appreciated!
Thank you! :smile:
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Avatar for Borek
Borek
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Start with ammonia molecule - is it neutral? Does it have a lone pair?

Now remove one proton. What is the charge of what is left? How many lone pairs now?
Original post by Borek
Start with ammonia molecule - is it neutral? Does it have a lone pair?

Now remove one proton. What is the charge of what is left? How many lone pairs now?


Thanks, that makes it a lot clearer.
I'm still a bit confused though. I understand why you would remove a proton, but isn't an electron lost too? Would the bonding in NH2 consist of a dative bond and a normal covalent bond??


Thank you :smile:
Original post by mr_brightside_
Thanks, that makes it a lot clearer.
I'm still a bit confused though. I understand why you would remove a proton, but isn't an electron lost too? Would the bonding in NH2 consist of a dative bond and a normal covalent bond??


Thank you :smile:


By "remove a proton" he means "remove a hydrogen ion" which means the same thing.

And because it's an ion, it means the electron stays behind.

NH4 would be + charged (dative covalent bond between N and an H+ ion)
NH3 is neutral
so NH2 must be negative otherwise the octet isn't filled.

As for shapes, you should be able to work out the shape of an atom with that many bonds and lone pairs.

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