Here in this article, we discuss only the NH3 lewis dot structure, its hybridization, shape, and molecular fact in detail, and the NH3Cl+ lewis dot structure.
In the NH3 lewis dot structure, N formed three sigma bonds with three H atoms. In this structure, N has three bond pairs and one lone pair. The lone pair is also involved in the hybridization and present one of the hybrid orbitals in sp3 hybridization. Though the molecule is sp3 hybridization so it is expected that the bond angle should be 109.50 but here H-N-H bond angle is 1070. So here lone pair-bond pair repulsion will be observed.
As it is sp3 hybridized so the shape of the molecule will be tetrahedral but it adopts trigonal pyramidal geometry. All the N-H bond lengths are equal and the value is 100.8 pm. In CFT, NH3 can behave as a good ligand and it can bind with a higher or lower oxidation state of metal.
Some facts about NH3
NH3 is a colorless gas in a physical state and has a distinct pungent smell. Scientist Haber 1st synthesized ammonia from nitrogen and hydrogen gas. It is very lighter than air, the density of ammonia is half of normal air. The molar mass of the ammonia molecule is 17.031 g/mol.
The melting point and boiling point of the ammonia molecule are 195.42 K and 239.81 K respectively. The vapor pressure of the gaseous ammonia molecule is 857.3 KPa.
In the Haber process, ammonia can be synthesized in industry.
2N2 + 3H2 = 2NH3
In different fertilizers, ammonia can be used, and it is a good source of nitrogen as well.
How to draw NH3 lewis dot structure?
To draw the lewis dot or lewis structure of a molecule is a very challenging as well as an important task. Because this lewis dot structure of a molecule can give us the proper basic information about the molecules like shape, bond angle, hybridization, valence electrons, etc. Before starting to draw the NH3 lewis dot structure there are a few many rules we have to follow.
Step 1– we should count all valence electrons for all the individual atoms in the molecule and add them together. In the NH3 lewis dot structure, there are Four atoms present, one N and three H atoms. The valence electrons for N are 5 and for three H atoms are 3. So, the total valence electrons are 5+3 = 8.
Step 2 – According to the octet rule, the electrons that will be needed for the NH3 lewis dot structure will be 8 + (3*2) = 14. The available valence electrons are 8. Now the required electrons will be (14-8) = 6 electrons and the minimum number of bonds required in this molecule is 6/2 = 3 bonds.
Step 3– Now we have to select the central atom. N is here central atom based on electronegativity and the size of the atom.
Step 4 – joining all the atoms with the central atom via the required number of single bonds i.e. three. So, N makes three single bonds with three H atoms.
Step 5– Now assigned the lone pairs over the respective atom. Here only N contains lone pairs, so the lone pairs are assigned over N only. Now if necessary, to require multiple bonds then only add multiple bonds but here octet is complete. So, no need to add multiple bonds or add any charge over the molecule.
NH3 lewis structure shape
In the NH3 lewis dot structure, 8 electrons will be involved in the whole bond formation. So, we can say that the electrons count for this molecule is 8, and according to the VSEPR theory, it adopts a tetrahedral shape.
According to the VSEPR (Valence Shell Electrons Pair Repulsion) theory if the electrons count for a molecule is 8 then it adopts tetrahedral geometry. But the condition is that the central atom has no lone pairs. In the NH3 lewis dot structure, central N has lone pairs, so it does not adopt tetrahedral geometry, rather it adopts trigonal pyramidal shape.
N is present at the central position and three H are at the three vertices of this geometry to maintain the structure.
NH3 formal charge
A molecule whether partially charged or not can be calculated by the formal charge. The formal charge is a hypothetical concept by which we can determine the charging property of the molecule.
It is a theoretical concept, so formal charge has a specific formula, and the formula is,
F.C. = Nv – Nl.p. -1/2 Nb.p.
Where Nv is the number of electrons in the valence shell or outermost orbital, Nl.p is the number of electrons in the lone pair, and Nb.p is the total number of electrons that are involved in the bond formation only.
There is an assumption for calculating formal charge that all the atoms have the same electronegativity.
In the NH3 lewis dot structure, there are N and H two different substituents present so we have to calculate the formal charge for both individually.
The formal charge over the N atom is, 5-2-(6/2) = 0
The formal charge over the H atoms is, 2-0-(2/2) = 0
From the calculation of formal charge, we can conclude that the NH3 molecule is neutral and no charge appears in it.
NH3 lone pairs
After bond formation, if there are pairs of electrons present in the valence shell of an atom are called lone pairs. Lone pairs are valence electrons but do not participate in the bond formation with other subsequent. NH3 has lone pair also.
To find out the lone pairs we have to check the electronic configuration of every atom in the NH3 lewis dot structure.
In NH3 lewis dot structure, H and N are only present so we have to check their electronic configuration.
H has only 1 electron in its s orbital and this is its valence electron. The lone pair needs at least two electrons but H has only 1 electron and that electron is involved in the bond formation. Naturally, H has no lone pair.
Except for H, there is another atom present N. N is the group 15th element in the periodic table. From its electronic configuration, we know that there are five electrons in its valence shell, so in N there may be a possibility of having lone pair. N formed three single bonds with three H atoms and used its three electrons from the valence shell.
So, now N has two electrons in its valence shell and there is no chance for further bond formation and those two electrons exist as lone pair in the NH3 lewis dot structure. So, the lone pair in the NH3 molecule is actually from the N site. These lone pairs are present in the hybrid orbital of the NH3 molecule and for this lone pair, the structure, and shape of the molecule differ.
So, in the NH3 molecule, lone pairs carry a significant role.
NH3 bond angle
The bond angle of a tetrahedral molecule is always 109.50 but in an NH3 molecule, the H-N-H bond angle will be 1070. So, there will be some deviation factor present in the NH3 lewis dot structure.
In the NH3 lewis dot structure, there is lone pair present in the hybrid orbital of N and three H atoms are also present there. Due to the small size of N, there is lone pair-bond pair repulsion that occurs in the NH3 molecule. To minimize the repulsion N decreases the bond angle to 1070.
Though it is a tetrahedral molecule its electronic shape is trigonal pyramidal and therefore its bond angle will be 1200. But due to lone pair-bond pair repulsion, it adjusted to 1070.
NH3 hybridization
N is from group 15th element whereas H is group 1st element. So, the energy of the orbital is different and not compatible with bond formation. So, they must undergo hybridization to form a new hybrid orbital of equivalent energy. Here N undergoes sp3 hybridization.
To calculate the hybridization, we use a specific formula, H = 0.5(V+M-C+A), where H= hybridization value of the central atom, V is the number of valence electrons in the central atom, M = monovalent atoms, C=no. of cation, A=no. of the anion.
In the NH3 lewis dot structure, the central atom N has five valence electrons including lone pair, and three H atoms are present in the surrounding.
So, the hybridization of central N in the NH3 molecule is, ½(5+3+0+0) =4 (sp3)
| Structure | Hybridization value | State of hybridization of central atom | Bond angle |
| Linear | 2 | sp /sd / pd | 1800 |
| Planner trigonal | 3 | sp2 | 1200 |
| Tetrahedral | 4 | sd3/ sp3 | 109.50 |
| Trigonal bipyramidal | 5 | sp3d/dsp3 | 900 (axial), 1200(equatorial) |
| Octahedral | 6 | sp3d2/ d2sp3 | 900 |
| Pentagonal bipyramidal | 7 | sp3d3/d3sp3 | 900,720 |
From the hybridization chart we can say that if the number of orbitals included in hybridization is equal to four then the central atom will be sp3 hybridized.
From the box diagram of the NH3 molecule, it is evident that the lone pair is also involved in the hybridization. The lone pair is present in the s orbital of the N atom. It is no longer present in the 3s orbital it is present sp3 hybrid orbital so it can be donated easily. That’s why NH3 can behave as a strong lewis base.
Conclusion
In the NH3 lewis dot structure, molecule is tetrahedral by geometrical shape but electron geometry is trigonal pyramidal. The bond angle is 1070 instead of 109.50. the molecule is polar due to an asymmetric structure. It can behave as a strong lewis base due to easily donation of lone pairs present in one of a hybrid orbital.
Hi……I am Biswarup Chandra Dey, I have completed my Master’s in Chemistry from the Central University of Punjab. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.
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