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I am learning the basics of bonding and reading about valence and lone electron pairs. I am confused on why nitrogen would bond 4 atoms of hydrogen such as in ammonium chloride. To me nitrogen has a valence of 3 so it can only form 3 bonds yet in NH4Cl it forms 4 bonds. Why would this be? Is this a concept of electronegativity? Furthermore in my book it states that the ions of NH4Cl are NH4+ and Cl-. Obviously the NH4+ has a positive charge but is this because it gives one electron to the Cl atom in the bond NH4Cl? Very basic but trying to grasp concepts.

When NH4Cl is in water, what pulls these two apart to create the cation NH4+ and Cl-? Are the bonds that these form with water stronger than the bonds between the NH4 and Cl so much so to pull them apart?

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$\ce{NH3}$ has a lone pair, so it forms a dative bond with $\ce{H+}$ by donating that pair to the bond between them.


As you have suspected, water pulls them apart. Water is polar, meaning that it has an unbalanced slightly positive charge near the $\ce{H}$ and an unbalanced slightly negative charge near the $\ce{O}$. These charges are responsible for dissolving.

Actually, the process of dissolution for is endothermic specifically to $\ce{NH4Cl}$, meaning that it takes more energy to dissolve it more than it gives. Other water-soluble chemicals like $\ce{NaCl}$ usually gives more energy in dissolving than it takes, making it exothermic.

Then what pulls them apart? Entropy. Search for "Gibb's free energy" for more information.

$\ce{NH4+}$ is not particularly stable as this is reversible:

$$\ce{NH4+ + H2O <=> NH3 + H3O+}$$

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NH3 is a base and when it is reacted with hydrogen chloride gas, hyrdochloric acid it form NH4Cl (NH3 + HCl → NH4Cl).

NH3 form NH4+ upon accepting one proton from HCl, as HCl is strong acid, it exist in the form of H+ and Cl- ion. Nh4Cl is formed due to electrostatic force btw NH+ and Cl-.

There is no loss and gain of electron, you are confusing it with ionic in which one atom loss electron and other atom gain electron to form bond( There is no loss of electron from NH4+ and again of Electron by Cl-).

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  • $\begingroup$ Two ways of understanding. 1: H gives electron to Cl and then N to H, so indirect electron transfer. 2: proton transfer instead of electron transfer as you stated. $\endgroup$ – DHMO Sep 8 '16 at 23:13
  • $\begingroup$ If you react with hydrochloric acid instead of hydrogen chloride gas (who would use hydrogen chloride gas instead of the acid), the electron transfer is more succinct. $\endgroup$ – DHMO Sep 8 '16 at 23:15
  • $\begingroup$ @user34388, NH3 it self is a gas, unless it's in the form of solution. $\endgroup$ – Khan Sep 8 '16 at 23:34
  • $\begingroup$ So if you combine NH3 + HCL the bonding is done by a proton transfer or indirect electron transfer and if so, what "H" gives the Cl the electron? $\endgroup$ – Atticus283blink Sep 8 '16 at 23:46
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    $\begingroup$ @user34388 I think i found the answer, do you agree with this here: imgur.com/j61r86o $\endgroup$ – Atticus283blink Sep 8 '16 at 23:51
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NH4Cl is example of a compound having dative, covalent and ionic bond. As far as your question is concerned N make 4 bonds by sharing 3 electrons with three H atoms and giving a pair of electrons to H+(dative bond) and whole molecule acquire a charge of +1.As far as dissociation of NH4Cl in water is concerned you will need knowledge of entropy, hydration energy and bond enthalpy etc.

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