Why isn't the ion NH4+ capable of hydrogen bonding?

[dramadeur]

If you draw lewis structure, central atom (N) will have 1 lone pair and 4 single bonds with Hydrogen.
Why can't hydrogen in this ion molecule be able to form hydrogen bonding with other molecules alike?
Is it because there's only 1 electron on the central atom?See for yourself: 5N + 4H -1 = 9 electrons to go around.
4 bonds = 8 electrons
9 - 8 electrons = 1 electron left.
So this 1 electron is placed on the central atom.

 

[Borek]

If you draw lewis structure, central atom (N) will have 1 lone pair and 4 single bonds with Hydrogen.

That's definitely wrong. No lone pair in NH₄⁺.

 

[dramadeur]

That's definitely wrong. No lone pair in NH₄⁺.

I've just updated my post. How can't there be?
Nitrogen has 5 valence e + 4 Hydrogen valence e -1 from the charge sign = 9 electrons to go around.
So... there's only 1 electron on the central atom?

 

[Borek]

5+4-1 is 9?

 

[dramadeur]

Yeah I dun goofed, sorry.
Anyway, if this molecule was just NH₄, and it had 9 molecules, would it be capable of hydrogen bonding? Since it would have a electron on its central atom...

 

[DrStupid]

Anyway, if this molecule was just NH₄, and it had 9 molecules, would it be capable of hydrogen bonding? Since it would have a electron on its central atom...

There is no atom orbital left to form a hydrogen bond. In NH₄⁺ there are four binding sp³ hybride orbitals populated with each 2 electrons. An additional electron would be located in an anti-binding sp³ orbital resulting in a half bond for one of the four hydrogen atoms. I do not know if such a molecule exists, but it would be less stable than NH₄⁺.

 

[Altered State]

Just imagine that the lone pair that is necesary to form hydrogen bonding which is present on NH₃, it is not present on NH₄⁺, becasue "it's forming the bond with the fourth hydrogen".

 

[DrStupid]

Just imagine that the lone pair that is necesary to form hydrogen bonding which is present on NH₃, it is not present on NH₄⁺, becasue "it's forming the bond with the fourth hydrogen".

However, that only means that NH₄⁺ cannot form a hydrogen bond with another NH₄⁺. But it can form a hydrogen bond with the electron pair of NH₃ resulting in [H₃N-H...NH₃]⁺.

 

[dramadeur]

There is no atom orbital left to form a hydrogen bond. In NH₄⁺ there are four binding sp³ hybride orbitals populated with each 2 electrons. An additional electron would be located in an anti-binding sp³ orbital resulting in a half bond for one of the four hydrogen atoms. I do not know if such a molecule exists, but it would be less stable than NH₄⁺.

Uhm... I said NH₄ not NH₄⁺
What will the lewis structure be? Will it have 1 electron on the central atom?

 

[Altered State]

Uhm... I said NH₄ not NH₄⁺
What will the lewis structure be? Will it have 1 electron on the central atom?

NH4 will not exist.
If an NH3 molecule binds to another atom/molecule, a positive charge will be held by the nitrogen.

 

[dramadeur]

NH4 will not exist.

But what would happen to a single left out electron in any atom where it's possible? Would it be placed on the central atom... or? Where would it go?

 

[Altered State]

But what would happen to a single left out electron in any atom where it's possible? Would it be placed on the central atom... or? Where would it go?

It is more complicated than that, electrons are not placed in "concrete spots" of the molecules, you can say that they are in a given molecular orbital.
But for sake of simplification, you can say that in that hypothetical situation, the electron could be on the central atom and you would have an ammonia/ammonium radical. A radical is a species that happens to have 1 single electron in one atom.
This is not a common thing in a molecule like ammonia, but there are many radical forms of organic molecules, for example: http://www.masterorganicchemistry.com/2013/07/30/free-radical-reactions/