Hybridization of NO₃ (Nitrate)

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What is the Hybridization of Nitrate Ion?

The easiest way to determine the hybridization of nitrate is by drawing the Lewis structure. After drawing the structure, we need to count the number of electron pairs, and the bonds exist in the central nitrogen atom. If we see NO3-, the central atom is bonded with three oxygen atoms, and there exist no lone pairs. Moreover, if we check the Lewis structure further, one of the nitrogen-oxygen bonds is a double bond besides the other two are of single bonds.

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The three sp2 orbitals of nitrogen overlap with one s orbital of the oxygen atom during bonding. The p orbital of nitrogen produces a double bond with three oxygen atoms where the three electron pairs are shared between the p orbital of the nitrogen and one p orbital of oxygen atom each. The oxygen atoms will also have two p orbitals that will accommodate a lone pair of electrons.


NO3 Molecular Geometry and Bond Angles

There is one central atom in nitrate which is surrounded by 3 identically-bonded oxygen atoms that lie at the triangle corners and a similar one-dimensional plane. In essence, nitrate has 3 electron domains with zero lone pairs. Thus, NO3-  molecular geometry is trigonal planar and is slightly bent. The bond angle is 120°.


Name of the Molecule

Nitrate

Molecular Formula

NO3-

Hybridization Type

sp2

Bond Angle

120°

Geometry

Trigonal Planar


Hybridization of the Central Atom in NO3-

To know the central atom's hybridization in NO3-, let us take the approach of drawing the Lewis structure of it, which looks like follows.

Now, without forgetting the '−,,' we need to calculate the number of electrons present in the NO3-.  We should then position the bonds with the right number of electrons and fill in the lone pairs around the atoms to get the right number of total electron count (electrons, represented as dots).

Now, by using the following table, we need to find the hybridization.

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Now, we should count the number of bonds between the atoms on the Lewis structure and then check the table. In the Lewis structure, we can see 3 bonds between the atoms (the dots show between atoms are the bonds).

Referring to the table under ‘type of hybrid orbital’, this is where the hybridization should be. It means, for ‘number of bonds’ = 3 and the hybridization is sp2. So, the result is sp2.

Bond Lengths Order For NO2+, NO2-, And NO3-

Let us calculate the bond orders before going to find the order. The higher the bond order results, the shorter the bond length.

So, Bond order= (Number of bonding electrons - Number of antibonding electrons)/2.

Now, to calculate these, we should consider the molecular order of a heteronuclear diatomic molecule NO first.

Now, NO molecule has 6 electrons in the bonding orbitals and 1 electron in the antibonding orbital. Thus, it has the bond order of (6–1)/2 = 2.5.

Then, NO2+ has 2 electrons, which is lesser than NO. It has 6 electrons in 4th bonding orbitals and zero electrons in antibonding. Thus it has the bond order of (6–0)/2 = 3.

For NO2-, the bond order is given by, (6–3)/2=1.5, and

For NO3- the bond order is given by (6–4)/2=1.

The order of the bond order can be given by, NO2+ > NO2- > NO3-

Thus, the order of bond length becomes NO3- > NO2- > NO2+.


Molecular Structure of NO3-

Since the nitrate ion comes from the nitric acid, so let us start from the structure of nitric acid.

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If we observe the bonding around the nitrogen carefully, we will see that one of the bonds is entirely formed from the lone pair on the nitrogen. That is called the coordinate bond.

The nitrate ion forms by the loss of the hydrogen ion and so its structure looks as below.

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There are 4 pairs of shared electrons around the central nitrogen and no lone pair remaining. Now, the original lone pair has become a bonding pair. So, two of those pairs form a double bond. The two single bonds and the double bond unit arrange themselves as far apart in a trigonal planar arrangement as possible - precisely similar to the carbonate ion, which is given below.

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State of Hybridization of N In NO3-

Let us discuss the sp3 hybrid orbitals of the central atom N. Here, the three sp2 orbitals present in a plane and form an arrangement of a trigonal plane. Each of these N-O bonds is produced by overlapping a nitrogen sp2 hybrid orbital and the oxygen 2p orbital. So, the molecule, NO3- is planar, and all the ONO angles become 120°.

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Uses of NO3

Some of the uses of nitrate are listed below.

  • The nitrate (NO3) can be used as an organic or inorganic ester or salt of nitric acid, containing the (NO3-) ion.

  • Of all salts, nitrates are the most soluble in water and play a significant role in the nitrogen cycle and nitrate pollution as well.

  • The inorganic nitrates are formed by the bacteria and are essential components of agricultural soil.

  • Nitrate is an essential chemical in the agricultural industry.

  • It is also an essential plant nutrient that assists in the plants' growth and processes, such as photosynthesis.

FAQ (Frequently Asked Questions)

1. Explain the Structure of Nitrate Ions.

Ans: The anion is the nitric acid's conjugate base with one central nitrogen atom surrounded by 3 identically bonded oxygen atoms in an arrangement of a trigonal planar. In general, the nitrate ion carries a formal charge of −1. This charge results from a formal charge combination in which each of the three oxygens carries a charge of −​2⁄3. In contrast, the nitrogen carries a charge of +1, adding up all these to the polyatomic nitrate ion's formal charge. Commonly, this arrangement is used as an example of resonance. Similar to isoelectronic carbonate ions, the nitrate ion can be represented by the resonance structures, as given below.

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2. Explain the Occurrence and Production of Nitrate.

Ans:  

  • Nitrate salts are naturally found on earth as large deposits, specifically of nitratine, which is a significant source of sodium nitrate.

  • Several nitrifying bacteria species form nitrates and the nitrate compounds for gunpowder were produced historically, in the absence of mineral nitrate sources and using different fermentation processes using dung and urine.

  • As a lightning strikes' byproduct in the earth's nitrogen-oxygen rich atmosphere, the nitric acid is produced when the nitrogen dioxide reacts with water vapour.

  • Nitrates are produced industrially from the nitric acid.