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

In summary, the ion NH4+ is not capable of hydrogen bonding because it lacks a lone pair of electrons on the central nitrogen atom. Hydrogen bonding occurs between a hydrogen atom bonded to a highly electronegative atom, such as nitrogen, oxygen, or fluorine, and a lone pair of electrons on another molecule. Without a lone pair, NH4+ cannot participate in hydrogen bonding, making it a weaker intermolecular force compared to other molecules that can form hydrogen bonds. This is why NH4+ is not as soluble in water and does not have as high of a boiling point as other molecules with the same number of atoms.
  • #1
dramadeur
19
0
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.
 
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  • #2
dramadeur said:
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+.
 
  • #3
Borek said:
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?
 
  • #4
5+4-1 is 9?
 
  • #5
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...
 
  • #6
dramadeur said:
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+.
 
  • #7
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".
 
  • #8
Altered State said:
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]+.
 
  • #9
DrStupid said:
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?
 
  • #10
dramadeur said:
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.
 
  • #11
Altered State said:
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?
 
  • #12
dramadeur said:
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/
 

1. Why doesn't NH4+ have a lone pair of electrons?

NH4+ is a positively charged ion, also known as an ammonium ion. This means that it has lost one electron, resulting in a lack of a lone pair of electrons. The loss of this electron is what gives the ion its positive charge.

2. How does the lack of a lone pair of electrons affect NH4+'s ability to form hydrogen bonds?

Hydrogen bonds occur when a hydrogen atom is bonded to a highly electronegative atom, such as oxygen or nitrogen. In NH4+, the nitrogen atom already has a full octet of electrons and is not able to form any additional bonds. Without a lone pair of electrons, NH4+ cannot participate in hydrogen bonding.

3. Can NH4+ form any other type of bond?

NH4+ can still form covalent bonds with other atoms, as it has four valence electrons available for bonding. However, these bonds are not as strong as hydrogen bonds and do not have the same properties, such as the ability to form intermolecular forces.

4. Why is NH4+ still considered polar despite not being able to form hydrogen bonds?

While NH4+ cannot form hydrogen bonds, it is still considered a polar molecule because of its asymmetrical shape. The nitrogen atom has a higher electronegativity than the hydrogen atoms, resulting in a slight negative charge on the nitrogen and a slight positive charge on the hydrogens. This polarity allows NH4+ to participate in other types of intermolecular forces, such as dipole-dipole interactions.

5. Are there any other ions that can form hydrogen bonds?

Yes, there are other ions that can form hydrogen bonds. For example, the hydroxide ion (OH-) and the fluoride ion (F-) both have a lone pair of electrons and can participate in hydrogen bonding. These ions also have a negative charge, which allows them to attract positively charged hydrogen atoms in other molecules.

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