MO Diagram, CN Lewis Structure, Molecular Geometry, Hybridization, and Polarity

CN, sometimes known as cyanide, is an anion that exists as a pseudohalide. It is a member of the cyano group and consists of a triple-bonded carbon and nitrogen atom. It has a negative one charge and is the conjugate base of hydrogen cyanide (HCN).

Several bacteria and cyanogenic chemicals contribute to the emission of cyanides in the environment. CN- ion can be found in both organic and inorganic compounds, such as acetonitrile and potassium cyanide.

CN- ion-containing chemical compounds have numerous applications in the modern world. It has decreasing properties.

As HCN, we find application in gas chamber executions and pesticide manufacturing.

It is used for gold and silver mining as NCN. Cyanides have additional usage as food additives and in the jewellery industry.

However, cyanide salts are toxic and harmful to human beings. Additionally, a reaction with water can produce gases and spark a fire. It can result in asthma, bronchitis, acidosis, prenatal harm, and even cerebral edoema.

Let’s now examine the chemical bonds within a cyanide ion to gain a better understanding of its chemical and physical features.

CN Lewis Architecture

What exactly is the Lewis Structure?

If we examine the above diagram, we may observe that it is a sketch of an oxygen atom. Since an oxygen atom has an atomic number of 8, its outermost shell contains six electrons.

The outermost shell is known as the valence shell, and it controls the atom’s valency, or its ability to combine with other atoms to create molecules.

Lewis Structure is a simple and straightforward diagrammatic representation of a chemical compound’s intrinsic structure. Here, the valence electrons are represented by dots, and the type of bond established between the valence electrons is indicated by straight lines.

Lewis Structure does not provide a great deal of information regarding bonding, but it is the first step in determining the 3D molecular shape or the nature of hybridization.

Determining the Lewis Structure of the CN Ion

An anion of cyanide is composed of carbon and nitrogen.

As a member of group 4 or 14 on the periodic table, carbon possesses four valence electrons.

Nitrogen is a member of group 5/15 with a valency of 5.

In addition, we must account for the electron that gives the CN- ion its negative charge. total amount of valence electrons is 4 plus 5 plus 1, or 10.

As CN is a diatomic ion, the concept of a core atom does not apply.

Now we will create a simple sketch or skeleton schematic of the cyanide ion.

We have placed atomic symbols for both carbon and nitrogen here. We shall place electron dot notations moving forward.

We have placed all ten valence electrons surrounding the CN ionic molecule’s component atoms. The concept of octet fulfilment is now presented.

Octet rule/Octet fulfilment: Examining the periodic table.

The octet rule states that the main group elements, i.e., groups 1 through 17, tend to acquire the configuration of noble gases.

Here, carbon and nitrogen atoms are present. Both are likely to attain the octet configuration of neon (noble gas of the same period).

Nitrogen (N) has already reached octet completion according to the Lewis Structure depicted in the preceding image. However, carbon still possesses only four surrounding electrons.

Carbon now possesses six valence electrons. It has not yet reached Neon configuration.

Both the component carbon and nitrogen atoms have now completed their octets.

Formal Demand

Now, we shall determine the Formal Charges of the atoms included within the anion.

Formal Charge for Carbon equals 4 – 0.5*6 – 2 = -1.

For Nitrogen, Formal Charge = 5 – 0.5*6 – 2 = 0.

Since the elements are present in their least possible formal charge values, our Lewis Structure design for CN is the most appropriate.

In addition, the formal charge value is -1.

We have successfully attained the negative charge within the CN anion.

The Lewis Structure of the CN anion.

Molecular Geometry

Lewis Structure provides a two-dimensional representation of the molecular or ionic structure.

In addition, it enables us to predict the 3D molecular form of every molecule, which is the next step in comprehending chemical bonding. We will determine the molecular geometry using VSEPR theory.

VSEPR concept

VSEPR refers to the model of Valence Shell Electron Pair Repulsion.

This idea suggests that electrons tend to form a negatively charged cloud environment around the component atomic nuclei of a molecule.

Since these have like charges, they oppose each other, and to obtain a stable molecule, it is necessary to reduce these repulsive forces.

Here, electrons refer to both bound or paired electrons (BP) and lone or unpaired electrons (LP) (LP).

LP-LP > LP-BP > BP-BP ( in case of strength ).

CN- Molecular Geometry

When there are more than two atoms within the molecular structure, we must account for VSEPR notations and steric numbers.

There are only two component atoms in CN-.

According to VSEPR theory, the ion’s three-dimensional shape or geometry is linear.

For the production of the anion, both C and N have a symmetrical distribution of valence electrons. Additionally, the number of lone pairs on each is identical. Therefore, a linear geometry is required to decrease repulsion and achieve stability.

The angle of the bond is 180 degrees.

Polarity CN

What does the term polarity mean?

Polarity is an essential characteristic of all chemical molecules. It depends on how charges are separated. This quality is specified by a separate term known as electronegativity.

This can be determined by using the Pauling Electronegativity chart:

In this Pauling Electronegativity scale, trends in electronegativity value throughout groups and periods of the periodic table can be discerned.

Electronegativity is an atomic attribute that describes a substance’s propensity to acquire or gain more electrons for bond formation.

We get a non-polar molecule when two atoms of the same element combine to produce a homogeneous diatomic molecule with a linear layout and identical electronegativity values (e.g. Cl2). Here, there is no net dipole.

However, when two or more atoms of different elements combine to create a molecule, or when the molecular structure is asymmetric, we obtain a polar molecule in which the net dipole is not equal to zero ( e.g. H2O ).

Polar or Nonpolar Is the CN anion?

Let us now concentrate on the Cyanide anion.

If we examine the above Pauling chart, we can determine the electronegativity values of both C and N.

The electronegativity of carbon is 2.55 while that of nitrogen is 3.04.

Therefore, the difference is equal to 0.49.

If the difference is between 0.40 and 1.70, we consider the bond polar. In addition, carbon, which is somewhat more electropositive than nitrogen, has a partial + charge, whereas N has a – charge.

The triple bond is slightly polar, and the ionic nature of CN allows it to interact with polar solvents such as water.

polarity CN

CN Hybridization

In order to comprehend the nature of chemical bonds within a cyanide ion, we have previously learned how to draw a 2D Lewis Structure.

After this, we studied the 3D molecular geometry and bond angles of CN- to go a little deeper. We have also discussed the differential in electronegativity and polarity of the anion.

Now we will discuss one of the most fascinating and significant principles of chemical bonding: Orbital Hybridization

Orbital Hybridization

Atomic orbitals, or AOs, come in a variety of forms and kinds, including s, p, d, and f.

As we already know, orbitals are mathematical probability functions that indicate where electrons can exist in any place.

For hybridization to occur, AOs of the same atom must come together and fuse with about equal energies. This results in hybrid orbitals such as sp, sp2, sp3, sp3d, etc.

For instance, orbitals 1 s and 3 p combine to generate sp3 hybridization.

The hybrid orbitals will have identical energies.

Cross-pollination in CN

If we examine the Lewis Structure of CN-, we can observe that carbon and nitrogen have created a triple bond.

This indicates the bond consists of one sigma and two pi bonds. The pi bonds, which are produced by the side-by-side overlap of p orbitals, have no function in hybridization.

Steric number = Number of atoms bound to a molecule’s central atom + Number of lone pairs of electrons attached to the central atom

Steric Number equals 1 sigma plus 1 lone electron for both carbon and nitrogen.

Consequently, we can identify the hybridization as sp.

In the C N bond, the sp orbitals of both C and N join to produce the sigma bond.

Molecular Orbital Diagram

Molecular Orbital Theory differs from VBT and orbital hybridization in a few ways. Here, AOs from various atoms inside the molecule can combine to generate MOs, or molecular orbitals.

Valence electrons are therefore shared within the molecule.

These are the electrical configurations of both C and N:

Carbon (atomic no:6)

C: 1s2 2s2 2p2

Nitrogen (atomic no:7)

N: 1s2 2s2 2p3

In MO theory, there are orbitals that are non-bonding, anti-bonding, and bonding.

The four electrons found in 1s orbitals do not form bonds.

The orbitals and are bonding orbitals.

The orbitals *and * are antibonding orbitals.

The CN- ion’s MO diagram is shown below.

Conclusion

Several significant terms and concepts pertaining to the chemical bonding of the cyanide ion have been examined in depth.

Happy studying!

Read more: MO Diagram, O3 Lewis Structure, Molecular Geometry, and Hybridization

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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