NH4+ Lewis Structure: Drawings, Hybridization, Shape, Charges, Pairs, and Detailed fact


This article contains the NH4+ lewis structure and its hybridization, shape, bond angle, and detailed explanations.

In NH4+ lewis structure, the molecule is sp3 hybridized and has a bond angle of 109.50, so the molecule’s shape is tetrahedral. This structure has no double bond, so the molecule could not show a different resonance structure. There is a shortage of electrons over N in this molecule. So, the positive charge is on N only.

Some facts about NH4+

NH4+ is known as ammonium ion. It is a cationic form of ammonia. The molar mass of ammonium ion is 18.039 g/mol. The ammonium ion is a white and soluble salt. Ammonium ion behaves as a weak acid. The pka value is 9.25. The conjugate base is ammonia.

 The protonation of ammonia synthesizes ammonium ions.

NH4+ lewis structure
Synthesis of Ammonium ion

During the metabolism of animals, ammonium ions produce as a by-product. Ammonium ions behave similarly to alkali metals.

Method of drawing the Lewis structure for NH4+

We always count the total valence electron for every molecule to draw its lewis structure.

In NH4+ lewis structure, there are one N, and four H atoms are present. The central atom is decided by electronegativity, but four H atoms surround one N atom. So, the central atom is N here. All the H atoms make a single bond with the N atom. There is a shortage of electrons over N, so the positive charge of the molecule resides over N only.

The octet of H is completed by forming a single bond with N. Now. We added the valence electrons of N and four H atoms. The ammonium ion is cationic, so the equal number of the electron that is one electron should be removed from this molecule. After making the single bond, there is no lone pair in this molecule. A positive charge is put on N to complete its octet, so, no need to put a double or triple bond here.

N has five electrons in its outermost orbital. But here, only four electrons make a four sigma bond with four each H atom. So a positive charge resides on the N atom. Each H atom has one electron, and they are for a single bond with a single electron of the N atom.

NH4+ lewis structure shape

NH4+ Shape

In NH4+ lewis structure ,four H atoms surround the central N atom. The shape of this molecule is tetrahedral. Four H atoms are present in four corners of the tetrahedral site. 

There are four H atoms present so that the structure can be a square planner, but in square planner geometry, the bond angle of the molecule will be 900In tetrahedral geometry, the bond angle is 109.50. Increasing the bond angle will decrease repulsion as the N atom is small. The shape of the molecule also indicates the hybridization.

Again, from VSEPR theory, the total electron count for this molecule is (5+4-1) =8, so the molecule’s structure having an electron count of 8 is tetrahedral.

NH4+ valence electron

NH4+ valence electron

NH4+ lewis structure the distribution of electrons in N is 1s22s22p3, and  H atom is 1s1. So, there are five valence electrons for N and one for H atom. But there is a positive charge in this ammonium ion, which means an electron shortage here. N donates its one electron. The valence electrons of N are four and for four H atoms, the total valence electrons are 4. So total valence electron of ammonium ion is 4+ (1*4) =8.

NH4+ lewis structure formal charge

The following formula can calculate the formal charge of any molecule, 

F.C. = Nv – Nl.p. -1/2 Nb.p.

Nv = number of electrons in the valence shell of the free atom

Nl.p = number of electrons in lone pair

Nb.p = number of electrons involved in the bond formation.

NH4+ Formal Charge

F.C. of H atom = 1-0-2/2 =0

F.C. of N atom = 5-0-8/2 =1

NH4+ lewis structure as the molecule is ionic species, there will be a formal charge on the molecule equal to the number of positive charges, which is 1.

Generally, the formal charge is equal to its charge for ionic species.

Number of lone pairs in an NH4+ lewis structure

NH4+ lewis structure after the bond formation, if there are pairs of electrons in a single shell, it is considered a lone pair for an individual atom.

Among five valence electrons of N, four of them form a bond with four H atoms in this molecule. H atom contains only one electron. So, there is no chance that H contains lone pair. One electron of N in the valence shell is donated. So, the molecule is lack of lone pairs.

Hybridization of NH4 

Hybridization is mixing atomic orbitals of similar and different energy to give new hybrid orbitals.

NH4+ lewis structure for hybridization of NH4+, we should count the valence electron of the central atom that is N. In the ground state, the distribution of electron of N is 1s22s22p3

In an excited state, it donates one electron from its p orbital, and one electron fromthe s orbital will shift to this vacant p orbital. This way it has four single unpaired electrons in its valence shell. These four unpaired electrons, one from s and one from p orbital under hybridization with four single electrons of four H atoms. 

After mixing these orbitals, a new hybrid orbital sp3 is formed. So, the hybridization of this molecule is sp3.

Hybridization of NH4

The molecule is sp3 hybridized, so the molecule’s structure is tetrahedral. Here only the sigma bond is considered in hybridization.

The central N atom is single-bonded with surrounded by four H atoms only.

Structure     state of hybridization of central atom     Bond angle
Linear         sp /sd / pd    1800
Planner trigonal      sp2       1200
tetrahedral      sd3/ sp3   109.50
Trigonal bipyramidal      sp3d/dsp3   900 (axial), 1200(equatorial)
Octahedral                  sp3d2/ d2sp3    900
pentagonal bipyramidal         sp3d3/d3sp3   900,720

Again, from the table, we can see that the tetrahedral shape molecule will be sp3 hybridized. So, ammonium ion is sp3 hybridized.

NH4+ bond angle

As the central N atom is sp3 hybridized in ammonium ion, the H-N-H bond angle is expected to be 109.50.

NH4+ Bond Angle

In NH4 lewis structure there is no deviation from this original data cause there are no lone pairs present in this molecule, so there is no chance of lone pair-bond pair repulsion. Besides, N is small in size, and four H atoms are attached with a single bond. Due to the larger bond angle, there is no repulsion.

The VSEPR theory and hybridization table confirm that the bond angle in ammonium ion is 109.50.

NH4+ octet rule

The octet rule is to complete the valence shell by donating or accepting electrons and gaining the nearest noble gas configuration.

NH4+ lewis structure H has one electron. It forms a covalent bond with N by sharing one electron and completing its octet and gaining the electronic configuration as He. N has five electrons in its valence orbital. In ammonium, ion N forms four sigma bonds with four H atoms by sharing one electron. But its octet is not fulfilled. To satisfy its octet, one electron is required. So, a positive charge resides on the N atom only. This way, N and H complete their octet.

NH4+ resonance structure

NH4+ lewis structure contains no π bond. So, we cannot draw the resonance structure its cause there is no chance of shifting the electronic clouds. Even if there is no lone pair of electron density present, we can shift them to draw a resonating structure.

Uses of NH4

  • Ammonium ion maintains the acid-base balance in the human body. The kidney produces ammonium ions to combine with many anions in the body to maintain the acid-base balance.
  • Using ammonium ion, we can synthesize the quaternary ammonium salt which can use in phase transfer catalysts in many organic reactions.
  • Ammonium salt is highly soluble in water, using this fact we can use them as a cleaning agent, surfactant, etc.
  • It is a good Nitrogen source for many plants, so we can use it in soil, but in limiting conditions, the excess will be poisonous.

Frequently asked questions (FAQ)

Compare the N-H length in NH3 and NH4+.

NH4+ , 5+4-1 = 8 (tetrahedral) , NH3 5+3 = 8 (tetrahedral)

Using VSEPR, both NH3 and NH4+ should have a tetrahedral structure. In both cases, the N atoms should be in sp3 hybridized. In NH3, since the hybrid orbital win in which the lone pair is present is of greater “s” character (Bent’s rule), the hybrid orbital of N directed towards the 3 H atoms in NH3 will have lesser “s” character w.r.t. sp2This is unlike the case of ammonium, where all the hybrid orbitals of N are sp3 hybridized. Thu the N-H length in NH3 will be longer.

Compare the acidic character of NH3 and NH4+.

Ammonia is basic, it has lone pair to be donated in any vacant site of other species, So it behaves like a lewis base.

But in ammonium ion, there will be no lone pair, and it has a positive charge and has an extra proton, so it can easily release this proton and behave like an acid.

Compare the bond angle of NH3, NH4+, and NH2.

NH4+ > NH3 > NH2

For ammonium ion there is no lone pair, in ammonia molecule, there is one lone pair and for an for amino ion there are two pairs of lone pair. As the number of lone pairs increases, then the repulsion also increases, and to minimize the repulsion the bond angle decreases.

Biswarup Chandra Dey

Chemistry is not all about reading line by line and memorize, it is a concept to understand in easy way and here I am share with you the concept about chemistry which I learn because knowledge is worth to share it.

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