In coordinate bond, why doesn't the H^+ atom get a negative charge?

  • Thread starter HCverma
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  • #1
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Main Question or Discussion Point

In a coordinate bond, why H^+ atom don't get the negative charge? as an example [NH4]^+
If we split [NH4]^+, we get NH3 + H^+. In NH3, N and 3H atoms have completed their octet and H^+ accepts the lone pair of electrons from the N, As we know H^+ has no any electrons but a proton. If it receives two electrons from the N, out of the two electrons, one electron neutrals the H atom so H^+ changes to H and another is an extra electron, so the H atom changes to H^- ( here H^+ ion does not share an electron with N but it completely receives from the N). So it NH4^+ should be NH3^+-H^-
 

Answers and Replies

  • #2
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It would be NH32+. How much energy would you need to get two electrons from NH3 and how would the remaining electrons be arranged?

I assume this happens in water? Keep in mind that you don't actually get H+. You get H3O+.
 
  • #3
Borek
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Hint: count charges on all nucleons, count all electrons, that gives you the charge on the molecule. Doesn't matter where the electron exactly is.

If you count two electrons on H, you will be missing one on N.
 
  • #4
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Hint: count charges on all nucleons, count all electrons, that gives you the charge on the molecule. Doesn't matter where the electron exactly is.

If you count two electrons on H, you will be missing one on N.
you mean to say N will show 7 electrons and it has 8 protons. For this reason, here N^+ meant one extra proton?
 
  • #5
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It would be NH32+. How much energy would you need to get two electrons from NH3 and how would the remaining electrons be arranged?

I assume this happens in water? Keep in mind that you don't actually get H+. You get H3O+.
H2O + HCl = H3O+ + Cl-
NH3 + HCl = NH4+ + Cl-
Am I Correct?
 
  • #6
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H atoms sometimes do get negative charges, in compounds with elements less electronegative than H.
Such as LiBH4
 
  • #7
Borek
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you mean to say N will show 7 electrons and it has 8 protons. For this reason, here N^+ meant one extra proton?
More like one missing electron, but yes, 8 protons in nucleus and 7 electrons would mean N+.
 
  • #8
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More like one missing electron, but yes, 8 protons in nucleus and 7 electrons would mean N+.
I got it but what my problem is that if H+ receives two electrons, why does not it change to H- because it has two electrons now out of two electrons, one is for one proton, making the atom a neutral and another is an extra atom, making the atom negative. could you explain, please?
 
  • #9
Borek
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It doesn't have two electrons, it shares these electrons with nitrogen, effectively having just one of them.
 
  • #10
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I got it but what my problem is that if H+ receives two electrons
There is no H+ that would receive two electrons.
 
  • #11
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It doesn't have two electrons, it shares these electrons with nitrogen, effectively having just one of them.
How could it share electrons with N because N completely donates its lone pair of electrons to H+?
 
  • #12
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There is no H+ that would receive two electrons.
What do you mean by 'there is no H+ that would receive two electrons'? Could you explain, please?
 
  • #13
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What do you mean by 'there is no H+ that would receive two electrons'? Could you explain, please?
I don't understand what is unclear.
You asked "if H gets two electrons, then X" and asked why X is not the case. Simple: Because H doesn't get two electrons.
 
  • #14
TeethWhitener
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How could it share electrons with N because N completely donates its lone pair of electrons to H+?
Why do you believe this? It isn’t true.
There is no H+ that would receive two electrons.
I think @HCverma is thinking of the fact that the lone pair on N donates electron density to the proton, forming a dative bond (a covalent bond where both electrons come from one atom). However, this type of bond is still covalent (electrons are shared). He seems to think it will be ionic, in which case you’d have
$$NH_3 +H^+\rightarrow NH_3^{2+} +H^-$$
due to charge conservation, as @mfb mentioned before in post 2.
Edit: for clarity’s sake, what really happens is:
$$NH_3 +H^+\rightarrow NH_4^+$$
where all 4 N-H bonds are equivalent (and the formal positive charge is distributed evenly across the four hydrogens).
 
  • #15
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Why do you believe this? It isn’t true.

I think @HCverma is thinking of the fact that the lone pair on N donates electron density to the proton, forming a dative bond (a covalent bond where both electrons come from one atom). However, this type of bond is still covalent (electrons are shared). He seems to think it will be ionic, in which case you’d have
$$NH_3 +H^+\rightarrow NH_3^{2+} +H^-$$
due to charge conservation, as @mfb mentioned before in post 2.
Edit: for clarity’s sake, what really happens is:
$$NH_3 +H^+\rightarrow NH_4^+$$
where all 4 N-H bonds are equivalent (and the formal positive charge is distributed evenly across the four hydrogens).
Could you please explain your point below in more detail?
'where all 4 N-H bonds are equivalent (and the formal positive charge is distributed evenly across the four hydrogens)'
 
  • #16
TeethWhitener
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Could you please explain your point below in more detail?
'where all 4 N-H bonds are equivalent (and the formal positive charge is distributed evenly across the four hydrogens)'
I'm not sure what else there is to explain. All of the bonds in NH4+ are equivalent (equal length/equal strength). The Lewis structure has a formal positive charge on the nitrogen, but in reality, the positive charge is shared equally by the hydrogens.
 
  • #17
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I'm not sure what else there is to explain. All of the bonds in NH4+ are equivalent (equal length/equal strength). The Lewis structure has a formal positive charge on the nitrogen, but in reality, the positive charge is shared equally by the hydrogens.
Ok, then where the positive charge on the nitrogen comes from? As I know positive charge means a proton and an atom shows only positive charge if it has an electron less in numbers than the protons at the nucleus of the atom.
 
  • #18
Borek
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As I know positive charge means a proton and an atom shows only positive charge if it has an electron less in numbers than the protons at the nucleus of the atom.
It is exactly the same for a molecule - count all protons in all nuclei, count all electrons, see what total charge you get.
 
  • #19
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It is exactly the same for a molecule - count all protons in all nuclei, count all electrons, see what total charge you get.
N has 7 protons and 7 (own electrons) + 3 (from 3 H atoms) = 10 electrons. So there are 3 more electrons, still why N atom has a positive ion on it? Please explain
 
  • #20
Borek
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You asked not about ammonia, but about NH4+ produced by adding a proton to ammonia.

Sometimes I wonder if you are not just trolling.
 
  • #21
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The electrons from the hydrogen atoms are not located at the nitrogen atom.
 
  • #22
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You asked not about ammonia, but about NH4+ produced by adding a proton to ammonia.

Sometimes I wonder if you are not just trolling.
Ok, just let me clear. Then where does the proton come on N in NH4+? Which atom or atoms add a proton to N? Could you explain, please?
 
  • #23
Borek
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Ok, just let me clear. Then where does the proton come on N in NH4+? Which atom or atoms add a proton to N? Could you explain, please?
You wrote an example of how it can happen by yourself:

NH3 + HCl = NH4+ + Cl-
 
  • #24
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You wrote an example of how it can happen by yourself:
No, my question is that from where does N get extra proton so that it changes to N+?
 
  • #25
mjc123
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If N got an extra proton it would become O+. The ammonia molecule gains a proton (in the form of a hydrogen ion) to become NH4+. This has 11 protons and 10 electrons, so has a single positive charge.
 

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