Hybridization, Molecular Geometry, and the Lewis Structure of NH4+

Ammonia’s chemical formula is NH3. When an Ammonia atom undergoes protonation, meaning it loses one of its electrons and becomes positively charged, a positively charged polyatomic ion of Ammonium, or NH4+, is formed.

Nitrogen and Hydrogen combine to form a protonated Ammonium ion, or NH4+. The ion is a by-product of the following chemical reaction between a proton donor and Ammonia:

NH3     +    H+   ——>     NH4+

Structure of Lewis

The electrons in a molecule’s valence shell are arranged and presented in a simplified Lewis structure.

The arrangement of electrons in the isolated atoms of an element is depicted in a Lewis Structure. Electrons are shown as dots in the Lewis Structure.

A line with a dot at both ends, involving the participating electrons, represents a bond between two electrons.

The ultimate goal is to find a configuration that has the best electron arrangement while maintaining the formal charges and the octet rule.

It’s important to remember that the goal behind Lewis Structure isn’t to explain molecular geometry, bond formation, or electron sharing between two atoms of one or more elements.

What is NH4’s Lewis Structure?

NH4+ is made up of Nitrogen and Hydrogen, as previously stated. When we look at the periodic table, we can see that Hydrogen is in group 1.

This means Hydrogen only has one electron. Because NH4+ has four hydrogen atoms, it has four hydrogen electrons.

Nitrogen, on the other hand, has a valence electron count of 5 due to its position in the 5th group of the periodic table. It is negative one because the plus sign represents the absence of one electron.

When we add up the number of electrons, we get 14 + 51 – 1 = 4 + 5 – 1 = 8

As a result, we have 8 valence electrons.

We can distribute the four hydrogen atoms around the single nitrogen atom by keeping Nitrogen in the centre and considering Hydrogen’s position on the outside.

The chemical linkages are then set in place.

Our arrangement will be 2,4,6, and 8 because the NH4+ atom has 8 valence electrons.

Hydrogen simply requires two valence electrons, which it already has, according to the octet rule. Even Nitrogen, which requires eight electrons in the valence shell, has all eight, resulting in a complete outer shell.

The loss of an electron is shown by surrounding the Lewis structure with a + symbol.

NH4 Molecular Geometry

While the Lewis Structure depicts an atom of a molecule in two dimensions, molecular geometry is the viewing and design of atoms in three dimensions.

The goal of molecular geometry is to accurately describe the overall shape and structure of a molecule, including bond lengths, bond and torsional angles, and other geometrical parameters and variables that determine the shape and arrangement of an atom, and therefore a molecule.

The atomic attributes of an element, such as polarity, magnetism, reactivity, colour, biological potency, and 3-dimensional space alignment, can also be determined using molecular geometry.

The molecular geometry features of an atom aid in the knowledge of the element’s behaviour, utility, and reactivity.

Molecular structures can be characterised as linear, angular, trigonal planar, octahedral, or trigonal pyramidal, depending on their geometry.

Once you have the Lewis Structure of an atom, you can depict its 3-dimensional structure.

Tetrahedral refers to the three-dimensional geometrical structure of ammonium, NH4+. Nitrogen should have had 9 electrons because it had 5 valence shell electrons and 4 from Hydrogen.

However, because of the positive ion, the + sign dictates that NH4+ contains 8 valence shell electrons. This indicates that NH4+ has four pairs in total, all of which are bound by the four hydrogen atoms.

Because NH4+ is a cation, the bond angle between two hydrogen atoms is 109.5 degrees rather than 90 degrees, which is the maximum distance between them.

The letter ‘tetra’ stands for four, which is the number of bond pairs formed by nitrogen in Ammonia.

While this makes the molecule symmetrical, the bond polarity of each Nitrogen-Hydrogen bond cancels out, making it a non-polar molecule.

You can also refer to the previously prepared article on the polarity of NH4 for a better understanding.

The geometrical depiction of the NH4+ molecule is shown below.

The NH4 Hybridization Process

Hybridization is the process by which atomic orbits fuse to form new degraded hybrid orbitals, which alter the bonding characteristics and molecular shape of an element’s atoms.

It is based on the molecular and quantum mechanics of an atom and can be thought of as an extension of the valence bond notion.

When compared to the prior orbitals, these new ones may have different forms, energy, and so on. Changes in an atom’s orbital configuration are also caused via hybridization.

As postulated by the valence bond theory, such a structure originates from the necessity for a sophisticated geometry of atoms necessary for electrons to couple up and create distinct chemical bonds.

These hybrid orbitals, which are created when an atom is hybridised, are useful in explaining and comprehending an atom’s molecular geometry, atomic bond characteristics, and position in the atomic space.

Hybrid orbitals are formed when atomic orbitals with similar energies combine in the most prevalent instances.

While the development of molecular orbits is thought to be the result of the exchange of atomic orbits between distinct atoms, hybridization is thought to be the result of a mixture of different atomic orbits overlaying one another in varying fractions.

Hybrid orbitals are made up of atomic orbits with similar energy levels. This process can also incorporate half-filled and fully filled orbitals, as long as the energy level stays the same.

The orbitals with similar energies can mix during hybridization. sp, sp2, sp3, sp3d, sp3d2, sp3d3, and other hybridizations are the most common.

The valence shell of an ammonium ion created by the release of an electron has a total of 8 electrons.

Nitrogen and the four hydrogen atoms in NH4+ form four sigma bonds, three of which are covalent and the fourth a dative bond. There are no pi bonds in the NH4+ ion.

As a result, all four electrons in the atomic orbitals of the nitrogen atom’s outermost shell can engage in hybridization, resulting in SP3.

The following formula can also be used to determine an atom’s hybridization:

Number of Ion Pairs + Number of Sigma Bonds = Hybridization.

The hybridization value of Ammonium is 4 because it possesses 0 ion pairs and 4 sigma bonds. As a result, the NH4+ setup is SP3.


Lewis Structure, Molecular Geometry, and Hybridization are all important concepts in understanding the structure, geometry, and, as a result, behaviour of a substance, which is a direct result of the properties of the atoms in the associated element.

Ammonia, or NH3, is widely utilised as a fertiliser, a refrigerant gas, a water purifier, and in industrial manufacturing.

While the Lewis structure helps us comprehend the 2-dimensional arrangement, molecular geometry gives information on its structural features when it is converted to Ammonium. Hybridization gives the NH4+ atom stability, allowing it to be used in a variety of ways.

Read more: Lewis Structure of BeCl2, Molecular Geometry of BeCl2, Hybridization, Polarity, and MO Diagram

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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