NH3 and NH4+ are two seemingly similar species but they are different. Ammonia comprises of a central nitrogen atom, three hydrogen atoms, and no charge. On the other hand, ammonium comprises a central nitrogen atom, four hydrogen atoms and it carries a positive charge.
The ammonium ion, NH4+, reacts similarly to NH3. The major difference between them is the ionization and the acidity of NH4+ compared to the basic NH3. NH4+ is a covalent compound but readily forms ionic compounds with anions.
What is the charge of NH4+ by itself and when in combination with other molecules or elements in compounds?
Properties of NH4+
- Ammonium is a cation with the formula NH4+ and a molar mass of 18.039 g/mol
- It is slightly acidic with an acidity level of 9.25 pKa
- It has a tetrahedral structure with the hydrogen atoms in symmetrical bonds to the nitrogen atom
- Ammonium ion forms soluble salts with acids
- Also, it behaves a lot like the ions of alkali metals
What is the charge of NH4+?
NH4+ is a cation with a +1 charge. The ammonium ion is a product of the protonation of the ammonia molecule. The unshared electrons on the central nitrogen atom bond to the proton, thereby resulting in a positive charge on the entire molecule.
As the bond between the nitrogen and hydrogen atom forms, the electrons on the nitrogen move further away from the nucleus to give the resulting positive charge.
Furthermore, NH4+ acts as an acid because it can produce hydrogen ions (as acids do) upon dissociation. It is also known as the conjugate acid of ammonia, which is a weak base.
What is the formal charge of N in NH4+?
You can calculate the formal charge of an atom in a compound by the formula:
Formal charge (FC) = number of valence electrons (V) – number of non-bonding electrons (L) – number of bonding electrons divided by 2 (B/2)
That is, FC = V – L – B/2
Nitrogen has 5 valence electrons, 0 non-bonding electrons, and 8 bonding electrons.
FC = 5 – 0 – 8/2
FC = 5 – 4 = 1
What is the formal charge of H in NH4+?
FC = V – L – B/2
Each hydrogen in NH4+ has 1 valence electron, 0 non-bonding electrons, and 2 bonding electrons.
FC = 1 – 0 – 2/2
FC = 0
What is the charge of NH4+ in NH4OH?
The charge of NH4 in ammonium hydroxide, NH4OH is +1. But the overall charge on the compound is 0 because the opposite charges on the two ions, NH4+ and OH–, cancel out each other.
NH4OH consists of one ionic bond between the ions, three covalent bonds between the central nitrogen atom and three hydrogen atoms, and one coordinate bond between the central nitrogen atom and one hydrogen atom.
What is the charge of NH4+ in NH4Cl?
The charge of NH4+ in ammonium chloride, NH4Cl, is +1. The chlorine atom is a nonmetal with a -1 charge. NH4Cl is an ionic compound and the opposite charges cancel out each other to form a neutral compound.
The ionic bond between the cation, NH4+, and the anion, Cl–, is a result of NH4+ supplying Cl– the one more electron it needs to complete its valence shell. This electron comes from the outstanding electron on the central nitrogen atom.
However, NH4Cl consists of more than an ionic bond. The central nitrogen atom binds to the hydrogen atoms through covalent bonds since they are both nonmetals.
There are three covalent bonds between the nitrogen atom and three hydrogen atoms and one coordinate bond between the nitrogen atom and one hydrogen atom.
What is the charge of NH4+ in NH4NO3?
The ammonium ion in ammonium nitrate, NH4NO3, is +1. The nitrate ion has a -1 charge. Following the crisscross rule, the opposite charges will cancel out each other, thereby making the whole compound a neutral compound.
What reactions does NH4+ undergo?
Ammonium ion reacts with water to form a conjugate acid and a conjugate base
When NH4+ reacts with water, it forms NH3 and H3O+.
NH4+ + H2O ⇄ NH3 + H3O+
In the above reaction, NH4+ acts as an acid, and water is the base. The resulting products, NH3 and H3O+, are the conjugate base and conjugate acid, respectively.
Ammonium ion forms soluble salts with all anions
Ammonium ion readily forms soluble salts with anions except when it forms ammonium perchlorate (NH4ClO4) and ammonium hydrogen carbonate (NH4HCO3).
Some of the common ammonium salts are ammonium chloride (NH4Cl), ammonium nitrate (NH4NO3), and ammonium sulfate ((NH4)2SO4).
Step 1: NH3(aq) + H2O(l) ⇄ NH4+(aq) + OH–(aq)
Step 2: NH4+(aq) + OH–(aq) + HCl(aq) ⟶ NH4Cl(aq) + H2O(l)
Finally: NH3(aq) + HCl(aq) ⟶ NH4Cl(aq)
The rate of decomposition of ammonium salts differs by the anion it contains. For instance, salts such as ammonium chloride and ammonium hydrogen carbonate which do not contain anions that are oxidizing agents will decompose into ammonia and acid.
NH4Cl (s) → NH3 (g) + HCl(g)
On the other hand, salts that have oxidizing agents as their anions will be internally oxidized and reduced. For instance, ammonium nitrate will decompose into nitrogen, water, and oxygen.
2NH4NO3 (s) → 2N2(g) + 4H2O(g) + O2 (g) (at 338°F to 500°F)
Nitrification
Nitrification is an essential aerobic step in the nitrogen cycle that converts ammonium, first, into nitrites and further oxidizes the nitrites into nitrates.
These processes are carried out by two nitrifying bacteria called Nitrosomonas (ammonium to nitrites) and Nitrobacter (nitrites and nitrates).
The nitrification process is as follows:
Step 1: NH3 + O2 → NO2– + 3H+ + 2e–
Step 2: NO2– + H2O → NO3– + 2H+ +2e–
FAQs
What is the charge of NH4+ in (NH4)2SO4?
In (NH4)2SO4, there are two ammonium ions, each with a +1 charge to make an overall +2 charge. This +2 charge neutralizes the -2 charge of the sulfate radical it bonds with.
Is NH3 the same as NH4?
No, they are not. NH3 is a neutral ammonia atom, while NH4+ is the ammonium ion. Moreover, ammonium is a nonpolar molecule, unlike polar ammonia.
Ammonium is a product of the protonation of ammonia. This adds one more hydrogen to ammonia and it forms a tetrahedral structure with the hydrogen atoms in symmetrical bonds with the central nitrogen atom.
This symmetry cancels out the polarity on each N-H bond to form an overall nonpolar molecule.
What is the charge of NH3?
NH3 is a polar molecule. Unlike ammonium ions, it is unionized. NH3 has an uneven distribution of electrons; one positive end and one negative end.
This uneven distribution of electrons is due to the higher electronegativity of nitrogen that pulls the electrons away from hydrogen and towards it instead. As a result, nitrogen carries more negative charge while hydrogen carries a positive charge.
Conclusion
NH4+ is a polyatomic cation that behaves like an acid, although a weak acid. The ammonium ion is a product of a bond that forms between the unshared electrons on the nitrogen atom and the extra proton that gives it its positive charge.
Although the charge comes from the central nitrogen atom, the entire ammonium cation shares the charge because the different atoms come together to be one unit.
The charge on the ammonium ion makes it quite reactive and easily binds to anions to form soluble salts.
You can also expand your knowledge by learning about the charge of nitrogen.
Thanks for reading.