The ammonium ion is a positively charged ion (cation) having its chemical formula NH4+. It is formed by the protonation of the molecule of ammonia. Many of you may have doubts regarding the polarity of ammonium ion. So, in this article, I will make you understand whether ammonium ion is polar or not and will also cover its properties and applications.
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So, Is NH4+ Polar or Nonpolar? NH4+ (Ammonium ion) is nonpolar in nature because of the tetrahedral structure. All the four hydrogen atoms are symmetrically bonded to the nitrogen atom and cancel out the polarity of the N-H bonds resulting in a nonpolar NH4+ molecule.
The ammonium ion is produced by the protonation of ammonia. When ammonia is reacted with the proton donors.
H+ + NH3 —reduction of NH3——> NH4+
The reduction of ammonia molecule occurs with the addition of 1 hydrogen atom to form ammonium ion.
Ammonium ions are considered to be mildly basic because they react with bronsted bases to get back to the state of the ammonia molecule. The reaction is as below
NH4+ + B− —-oxidation of NH4+—> HB + NH3
The ammonium ion undergoes oxidation due to the removal of 1 hydrogen atom so as to form an ammonia molecule.
The extent up to which ammonia produces ammonium ions is dependent on the ph value of the solution.
When ammonia is dissolved in water, it dissociates into the ammonium ions. The equilibrium reaction is as below
H2O (water) + NH3 (ammonia) ⇌ OH− (hydroxideion) + NH4+ (ammmonium ion)
As discussed above, the concentration of ammonium ions depends upon the ph value of the solution. It means that if the ph value of the solution is low, the formation of ammonium ions is greater ie; equilibrium shifts in the right direction.
And if the ph value of the solution is more, the hydroxide ion takes out the hydrogen atom from ammonium ions to form ammonia ie; equilibrium shifts to the left.
If we talk about the chemical composition of ammonium ion, it consists of 4 hydrogen atoms and a nitrogen atom.
The nitrogen atom is the central atom surrounded by the four hydrogen atoms symmetrically in a tetrahedral arrangement.
The electronegativity of Nitrogen is 3.04 and that of hydrogen is 2.2. The difference between their electronegativity generates the polarity across the N-H bond.
As a result, the N-H bond is polar in the NH4+ molecule. The dipole value of NH4+ ions is also non zero.
But due to the symmetrical arrangement of N-H bonds, the dipoles get canceled out by each other resulting in a nonpolar molecule.
Difference Between Polar and Nonpolar Molecules?
The molecules that are covalently bonded with each other may have an overall unequal and equal distribution of charge over its atoms.
The polarity of a molecule is to be checked with various parameters that we will discuss later below
Polar molecules: These are the molecules that have poles generated in them. The two poles are positive and negative.
The atoms in these molecules do not have an equal distribution of charge on them.
Two atoms that are covalently bonded form a polar bond if they both differ in their electronegativity.
A higher electronegative atom becomes a negative pole and the lower electronegative atom becomes a positive pole.
The value of the net dipole moment of such molecules turns out to be non zero. Some of the examples of polar molecules are OF2, PF3.etc. You can check out the reason for the polarity of PF3.
Nonpolar Molecules: These molecules do not generate any poles across it. The distribution of charge over the atoms in these molecules is uniform.
The atoms covalently bonded form a nonpolar bond if the electronegativity of both atoms is equal. This is because both atoms share an equal proportion of charge.
It is also possible that a nonpolar molecule consists of polar bonds within it, but their polarity gets cancel out with each other due to geometrical symmetric shape.
Some example of nonpolar molecules is BH3, BeCl2, etc. You can check out the reason for the polarity of BH3.
Why is NH4+ nonpolar?
As studied above, the nitrogen atom lies at the center and all 4 hydrogen atoms are arranged in the four corners of the trigonal pyramidal.
The N-H bond has some value of dipole but all the four dipoles are in different directions and due to the symmetrical shape of NH4+ molecule, the 4 dipoles cancel out each other making the NH4+ a nonpolar molecule.
Therefore, it should be noted that it can be possible for a molecule to be nonpolar even if it consists of polar bonds within it because the dipoles get canceled out by each other.
Lewis and Geometrical Structure of NH4+
As we know nitrogen has 5 valence electrons and requires 3 electrons to complete its octet. On the other hand, hydrogen has 1 valence electron and requires 1 more electron to get stable.
So, all four hydrogen atoms share their single electron with nitrogen. With this, all hydrogen gets stabilized.
And nitrogen has (5 + 4) electrons ie; 9 electrons and + sign on NH4+ means that it loses one electron.So total electrons with nitrogen in its outermost shell becomes 9-1 = 8 electrons ie; octet complete.
And with this, the nitrogen atom also gets stabilized.
And the four bonds are in tetrahedral in shape. The bond angle of H-N-H is around 109.5 degrees.
All four N-H bonds are symmetrical to each other. Below is the image of the geometrical shape of ammonium ion.
For more detailed information about lewis structure, you can also read out an article on lewis structure of NH4+.
Parameters that determine the polarity of a molecule
There are a few parameters that are required to check whether a molecule is polar or not.
Let us discuss one by one.
Electronegativity: The term electronegativity depicts the value of the strength of an atom to attract the bonded electron pair towards its side.
The polarity across a covalent bond formed between two atoms ensures the difference between their electronegativity and vice versa.
The polarity of a molecule is directly proportional to the electronegativity difference between atoms forming it.
Dipole Moment: The dipole of a molecule is the measure of its polarity. The polar molecule always has its dipole equals to non zero.
And the nonpolar molecules have net dipole equals to zero. Its SI unit is Debye and is denoted by D.
Similarly, the dipole of NH4+ (Ammonium ion) is 0 D.
Geometrical Shape: If a molecule is symmetric in shape then the molecule tends to be nonpolar in nature whereas the asymmetric molecules tend to be polar.
Similarly, ammonium ion is symmetrical tetrahedral in shape due to which the polarity of N-H bonds gets canceled out.
Properties of NH4+
The molecular mass of ammonium is 18.039 g·mol−1.Formal charge over ammonium ion is 1.Its acidity is 9.25 PKA.The molecular shape of this cation is tetrahedral.
Uses of NH4+
The compounds formed by the ammonium ions are widely used in the production of fertilizers.The ammonium compounds have great use in medicines and in textile industries.
The ammonium ion is tetrahedral in shape ie; all the N-h bonds are arranged symmetrically over the nitrogen atom.
Nitrogen and hydrogen differ in their electronegativity. As a result, the N-H bond is polar and results in some no zero value of dipole moment.
But the dipoles of N-h bonds get canceled by each other due to the symmetrical shape of ammonium ion resulting in the nonpolar NH4+ ion.
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