Ammonia (NH3); How to Draw Lewis Structure, Molecular Geometry, Hybridization, And MOT Diagram

Ammonia (NH3) (IUPAC Name is Azane). It is the most basic binary hydride composed of nitrogen and hydrogen, indicated by the chemical formula NH3. Ammonia is colourless, has less mass than air, and has a strong odour. It is a covalently linked stable pnictogen hydride.

NH3 is a typical nitrogenous waste of sea life and an essential component of terrestrial species’ nutritional needs. Furthermore, ammonia is corrosive and harmful when stored in large quantities.

This blog post covers detailed and concise knowledge about the Lewis structure, molecular geometry & shape, hybridization, bond angle, physical/chemical characteristics and uses of the NH3 molecule.

Molecule name Ammonia
Formula NH3
Electronic configuration 1s2, 2s2, 2p3
Valence shell electrons 8
NH3 hybridization Sp3
Molecular geometry Trigonal Pyramidal planar
Electron geometry of NH3 Tetrahedral
Dipole moment 1.46D
Bond angle 107.3⁰
The oxidation number of NH3 zero
NH3 Is polar or non-polar. Polar molecule

General Rules to Draw Lewis Structure

Table of Contents

  • Firstly, count all the valence electrons
  • Calculate the number of electrons required to make the atoms “happy.”(octet rule)
  • Calculate the number of bonds in the molecule
  • Select a Central Atom (having less electronegativity)
  • Construct a Skeletal Structure
  • Arrange Electrons Outside Atoms
  • Distribute the remaining electrons around the central atom.

How Atoms Arranged in Ammonia (NH3)

NH3 has three hydrogen atoms and a nitrogen atom with an unshared pair of electrons. It has strong intermolecular hydrogen bonding and polar properties. Ammonia (NH3) is formed when three atoms of hydrogen combine with one nitrogen atom.

Nitrogen contains 5 electrons in its valence shell, thus it must interact with 3 hydrogen atoms to meet the octet rule and produce ammonia, a stable molecule (NH3).

Before going towards the Lewis structure of ammonia, let’s understand some general terms used in it.

Valence Electron

Valence electrons are the total number of electrons present in the atom’s outermost shell. Only valence shell electrons involve in bond formation. These valence electrons either share or are transferred (completely or partially) for bond formation.

For example, in NH3 the outermost shell of nitrogen has five electrons. As a result, nitrogen has five total valence electrons. Similarly, hydrogen has one electron on its outermost shell, resulting in one valence electron.

The Formal Charge (FC)

The difference between each atom’s valence electrons and the number of electrons with which it is related is known as a formal charge.

The formula for determination of formal charge is

FC = V-N-B/2

Here;

V = no. of valence electrons

N = no. of nonbonded electrons

B = no. of bonded electrons

The Lewis diagram of any molecule will be more stable whenever the formal charge of an atom is lower.

http://scientificsarkar.com/structure-of-water-molecule/

Draw Lewis Structure of Ammonia (NH3) in 3 Easy Steps

The Lewis structure merely takes into account the electrons present in the valence shell, neglecting the inner shell’s electrons. A dot represents a lone pair of electrons in a Lewis structure, whereas a straight line indicates a bonded pair of electrons.

The Lewis structure of NH3 can draw in multiple segments, beginning with valence electrons of nitrogen and hydrogen atoms. This article goes through each step of sketching the Lewis structure of NH3. You can able to understand the geometry of the NH3 molecule after drawing the Lewis structure of NH3.

Step #1

Determine the Total Number of Valence Electrons

Ammonia is made of two elements: hydrogen and nitrogen. H is a group IA element with one electron in its outermost shell. Nitrogen is in-group VA of the periodic table with five electrons in its outermost shell.

To calculate the total outermost electrons of a particular element, multiply the number of atoms present in a particular element by its valence shell electrons.

Now let us calculate the Valence of Shell Electron of NH3.

  • For Nitrogen

As nitrogen is a VA element of the periodic table

Therefore, the valence electrons in the outermost shell of nitrogen are five

Valence electron (5)* no. of atom (1) =

  • For Hydrogen

As hydrogen is a 1A element of the periodic table

Therefore, the valence electrons of hydrogen are

Valence electron (1) * no. of atoms (3) =3

So, the total number of valence electrons presnet in NH3 molecule = 5+3 = 8

Step # 2

Identify the Central Atom

The capacity to have more valence electrons is essential for becoming the centre atom. Then, which of the hydrogen and nitrogen atoms has the greatest valence electrons?

Nitrogen has maximum valence electrons of five. Hydrogen has only one valence electron. As a result, the centre atom of NH3 should be nitrogen.

Now we can draw the NH3 structure to show how the atoms are connected by bonds in the molecule.

Step # 3

Put an Electron Pair Between the Atoms

After finding the central atom and drawing the NH3 molecule, we may begin to mark lone pairs on atoms. Remember that there are four electron pairs in total.

In the above image, there are three N-H bonds. Now just one electron pair is left to designate on atoms.

Typically, the electron pairs should begin to mark on external atoms. However, in NH3, the outer atoms are hydrogen atoms, which cannot hold more than two electrons in their outermost shell.

In hydrogen atoms, there are already two electrons. Therefore, it’s impossible to mark leftover electrons pair on the hydrogen atom.

Therefore, mark that electron pair on the central nitrogen.

Check the stability of NH3 by calculating the formal charge distribution on all atoms

Ammonia (NH3) has zero elevated charges. However, it does not have a chemical charge in reality. While it’s simple to say that, it’s essential to put an answer in this context and know what it meant in chemistry. It’s also important to understand how to determine an atom’s charge.

Let’s look at how formal charge is calculated and what it signifies.

The following is the equation for calculating an atom’s formal charge:

FC (formal charge) = V (No. of valence electrons) – N (No. of non- bonded electrons) – B (No. of bonded electrons) /2

Now let’s determine the Formal charge on ammonia (NH3)

Formal charge on N2 = (5)-(2) – (6)/2 = 0

Formal charge on H2 = (1) – (0) – (2)/2= 0

Ammonia has stable atoms because they form covalent bonds and have no formal charge. As we already know the smaller the formal charge, the more stable a molecule’s Lewis structure. The above structure is the best Lewis dot structure for the NH3 molecule since the ammonia (NH3) contains no formal charge on any of its atoms.

The Ammonia (NH3) Octet Rule

According to the octet rule, the maximum number of valence electrons that can be drawn around an atom’s symbol is eight.

The Lewis structure of NH3 is designed to satisfy and balance the lack of three valence electrons in the nitrogen atom and one valence electron in each hydrogen atom.

What exactly is the Lewis Structure?

A Lewis Structure is an extremely simple representation of a molecule’s valence shell electrons. It is used to illustrate how electrons in a molecule are organized around specific atoms. Electrons are generally, shown as “lines” or as “dots” between two atoms when they are bonded.

Why it’s Important to Know Lewis’s Structures?

Lewis structures are important in predicting the geometry, polarity, and reactivity of compounds (organic & inorganic). Knowing an atom’s Lewis structure helps you to predict how it will bond, and how many bonds it will make.

This information will ultimately help us to understand the structure of molecules as well as their chemical characteristics.

Molecular Geometry & Shape of Ammonia (NH3)

The three-dimensional (3D) arrangement of atoms linked together to form a molecule is called molecular geometry. To know the molecular geometry of any molecule is essential because it offers information on a variety of physical and chemical properties, such as polarity, phase of matter, reactivity, colour, biological activities, magnetism, and so on.

Ammonia (NH3) has three N-H bonds and one lone pair on the nitrogen atom in its Lewis structure. So, ammonia has a trigonal pyramidal planar shape. Trigonal pyramidal planar geometry of NH3 is due to the presence of lone pair of electrons on the central nitrogen atom. The pyramidal shape of NH3 is formed when nonbonding pairs of electrons push away by bonding pairs of electrons

VSEPR theory is also used to calculate the shape or geometry of the NH3 molecule. We could employ the AXN technique for the determination of NH3 geometry.

Determination of NH3 Geometry by AXN Method

In AXN,” A” shows the central atom. Ammonia has nitrogen at the centre so, A= Nitrogen (N2).

  • “X” represents the atoms bonded to a central atom. Three hydrogen atoms are bound to the central atom of nitrogen in the NH3 Therefore, X= 3
  • “N” donates the lone pair of electrons present on the central atom. There is only 1 lone pair on central nitrogen. So, N=1

However,

  • AXN (for NH3) = AX3N1 or (AX3).

If a molecule has an AX3N formula, it possesses trigonal pyramidal geometry, according to VSEPR theory. Therefore, AXN formula proves that NH3 has trigonal pyramidal planer geometry.

The Bond Angle of NH3

The bond angle is the angle formed by the central atom and the bounded atoms. The number of bonded atoms determines the Bond angle. A larger bond angle would be the result of less repulsion.

The bond angle of ammonia is 107 degrees. There are four electron-rich areas in the ammonia molecule (three N–H bonds and one lone pair of electrons on the centre N atom). The NH3 molecule’s shape is trigonal pyramidal due to these four electron-dense regions, resulting in a bond angle of 107°.

NH3 is a polar molecule

A polar molecule has uneven electronegativity among its constituent atoms. This causes an electric charge imbalance across the molecule, giving it a net dipole moment.

A polar covalent bond is established. If the electronegativity difference between the atoms is 0.5 – 2.

Following are the factors that determine the polarity of ammonia (NH3)

Molecular Geometry

The shape of any molecule is an important factor to depict the polarity of the molecule. Asymmetrical or distorted molecules are polar while molecule having symmetrical shape is non-polar in nature.

NH3 has asymmetrical trigonal pyramidal geometry; the deformed shape of ammonia is due to the lone pair of electrons, which exerts a force of repulsion on the bonding pairs. That is why it’s a polar molecule.

In addition, the bond angle for trigonal pyramidal molecular geometry should be 109.5⁰; however, it was lowered to 107⁰ due to lone pair of nitrogen.

Electronegativity of NH3

Electronegativity describes how strongly an atom attracts electrons in a chemical bonding. The electronegativity difference between two atoms determines the chemical bond.

  • If the electronegativity difference is more than 2.1, the bond will be ionic.
  • When the electronegativity difference is between 0.5 and 2.1, the bond will be polar covalent.
  • If the electronegativity difference between two atoms is less than 0.5, the bond will be non–polar.

The greater value of electronegativity makes the covalent bond polar. In NH3, electronegativity values for nitrogen and hydrogen are (3.04), and (2.2) respectively. The differences in electronegativity between both atoms (3.04-2.2 =0.84) make the N-H bond polar.

Dipole Moment

A dipole moment is an electrical charge separation measurement. The dipole moment is large for the bonded atom which has a more electronegativity difference.

NH3 is a polar molecule because it possesses three dipoles due to three bonds, and these dipoles do not cancel each other out. They interact to produce a net dipole moment which is around 1.46D

Ammonia (NH3) Molecule Hybridization

Hybridization is the process of combining atomic orbitals to generate hybrid orbitals, which are then used to build chemical bonds. The phenomenon of hybridization is essential because it allows us to predict the shape of a molecule.

In NH3, each nitrogen and hydrogen atom has a covalent link made up of one sigma bond and no pi bonds.

As we know, pi bonds are only found in double or triple bonds, whereas ammonia (NH3) possesses only single bonds.

Sigma bonds have the highest stability and are the most powerful covalent bonds.

Nitrogen hybridization in ammonia (NH3) is sp3. The nitrogen atom possesses one 2s and three 2p orbitals, which combine and overlap to generate four hybrid orbitals of equal energy, as seen in the graphic representation of hybridization in NH3.

The 3 bonding and one non-bonding hybrid orbitals involve in the ammonia’s sp3 hybridization. So, ammonia is sp3 hybridized.

Physical & Chemical Characteristics of Ammonia (NH3)

  • NH3 is a gas with non-toxic properties and a pungent smell.
  • Due to strong hydrogen bonding between a molecule, NH3 can liquefy easily.
  • It is an inorganic compound that gives nitric acid and water in reaction with O..
  • P of NH3 is -77.73 ⁰C
  • P is -33.34 ⁰C
  • Molar mass of NH3 is 17.03052g/mol
  • NH3 molecule has 0.73 kg/m3 density and 3 kPa vapour pressure at room temperature.

Uses of Ammonia (NH3)

  • More than 80% of ammonia is utilized as agricultural fertilizer across the world.
  • Ammonia is a powerful stain remover that is commonly used to clean stains from tiles, oil splatters on the stove, and other unclean surfaces.
  • NH3 help to clean mirrors and windows.
  • NH3 eliminates fingerprints and other stains from windows and mirrors in just a minute and leaves them gleaming.
  • Hydrogen cyanide, Hydroxylamine, Hydrazine, Ammonium carbonate, Phenol, Amino acids, Urea, and other chemicals are made from ammonia.
  • Ammonia solutions are utilized in the fermentation sector as nitrogen sources for microorganisms.
  • It’s also responsible for changing the pH in the fermentation process.
  • NH3 is used as an antiseptic.

Overview

In the lewis structure of NH3, single sigma bonds which are present between nitrogen and hydrogen are three.

Furthermore, the existence of a single lone pair of electrons on the nitrogen atom is responsible for the NH3 molecule’s bent geometrical shape. It is one of the reasons why the bond angle is 107° rather than 109.5°.

The method for constructing NH3 molecular geometry, the polarity of ammonia, the method for finding the lone pairs of electrons in the central nitrogen atom, and NH3 hybridization, are all described in this article. It’s important to note that if you use the method described above, you may simply make the NH3 molecular structure.

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FAQ’s

What does NH3 look like?

The NH3 molecule has a trigonal pyramidal form, with a bond angle of 107.3 degrees. NH3 is made from three N-H bonds with one lone pair on the nitrogen atom. The trigonal pyramidal geometry of NH3 is due to a lone pair of electrons that are present on the central nitrogen atom

Is NH3 tetrahedral or trigonal planer?

The resultant molecular shape is trigonal pyramidal when there is one lone pair of electrons and three bond pairs. For example, NH3. When the molecular geometry is trigonal pyramidal, the bond angle should be 109.5 degrees. But in NH3 the bond angle reduce to 107.3 degrees due to the lone pair on the central atom.

What type of bond is NH3?

As nitrogen and hydrogen both are non-metallic and do not tend to donate electrons. So, ammonia cannot has an ionic bond. NH3 has a single covalent bond between 1 nitrogen and 3 hydrogen atoms. As the covalent bond is formed when electrons are mutually shared between the two atoms. Nitrogen has five valence electrons of which three are shared with hydrogen atoms to form a covalent bond.

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