How to draw HCN Lewis Structure? - Science Education and Tutorials

Q: What is the HCN Lewis structure?

HCN Lewis structure is dot representation

Q: What is the formal charge on the HCN Lewis structure?

Zero charges on the HCN molecular structure

The hydrogen cyanide chemical formula is HCN. Drawing HCN Lewis Structure is very easy to by using the following method. Here in this post, we described step by step method to construct HCN Lewis Structure. The cyanide species(which contain carbon and nitrogen) and hydrogen elements come as the member of the halogen and hydrogen family groups from the periodic table respectively. The valence electrons in cyanide species and hydrogen are seven and one respectively. Hydrogen cyanide is used to make chemical reagents for organic chemical reactions as a cyanating agent in organic chemistry.

Table of Contents

Key Points To Consider When Drawing The HCN Electron Dot Structure

A three-step approach for drawing the HCN Lewis structure can be used. The first step is to sketch the Lewis structure of the HCN molecule, to add valence electrons around the cyanide species; the second step is to add valence electrons to the one hydrogen atom, and the final step is to combine the step1 and step2 to get the HCN Lewis Structure.

The HCN Lewis structure is a diagram that illustrates the number of valence electrons and bond electron pairs in the HCN molecule. The geometry of the HCN molecule can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory), which states that molecules will choose the HCN geometrical shape in which the electrons have from one another.

Finally, you must add their bond polarities to compute the strength of the one H-Br single bonds (dipole moment properties of the HCN molecule). The hydrogen-cyanide species bonds in hydrogen cyanide(HCN), for example, are polarised toward the more electronegative cyanide species in HCN molecule, and because both bonds have the same size and are located around one hydrogen terminal of the tetrahedral or linear structure with three lone pairs (in total six electrons) on the cyanide species, their sum of dipole moment is nonzero due to the HCN molecule’s bond dipole moment and less electron polarity to the hydrogen atoms. Because H-CN bonds polarity is not canceled in the HCN molecule due to the presence of three lone pairs of electrons in the tetrahedral structure. The hydrogen cyanide(HCN) molecule is classified as a polar molecule.

The molecule of hydrogen cyanide(with tetrahedral or linear-shaped molecular geometry) is tilted, the bond angles between cyanide species and hydrogen are 180 degrees. It has a difference in electronegativity values between cyanide species and hydrogen atoms, with central cyanide species pull being higher than terminal hydrogen’s in the HCN molecule. But they not canceled each other due to the asymmetrical linear structure with one lone pair of electron on nitrogen atom in the molecular geometry of the HCN molecule.

As a result, it has the nonzero dipole moment. The HCN molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges. But both cyanide species and hydrogen atoms fall on the carbon, nitrogen and hydrogen family groups in the periodic table respectively. The cyanide species(triple bond with carbon and nitrogen atoms) is a more electronegative value than hydrogen in the HCN molecule. The HCN molecule has the net dipole moment of 2.9 D value in the ground state energy level.

HCN molecule has one H-CN single bonds and triple bond between carbon and nitrogen. Its dipole moment in the ground state is totally different as compared with the excited state. If it absorbs light may be from visible or UV light. It undergoes pi to pi star and n to pi star transition from ground state energy level to excited state energy level. In the excited state energy level, the HCN molecule shows a definite dipole moment. But it is very dynamic in nature.

Molecules can be classified as polar or nonpolar. The molecule polar behaves in a different manner as compared to nonpolar.

Overview: HCN Lewis Structure

The central atom is a carbon (cyanide species), which is bordered on two terminals with hydrogen atoms( in tetrahedral or linear geometry), and three lone pairs on the central carbon atom ( cyanide species) in linear molecular geometry. Carbon in cyanide species has four outermost valence electrons, indicating that it possesses four electrons in its outermost shell, whereas hydrogen also has one valence electron in its outermost shell. Nitrogen has three valence outermost electron. Cynanide species triple bonded with carbon and nitrogen. To complete the octet of the cyanide species requires one valence electron on each of their outermost shell.

One hydrogen atom establishes covalent connections with the central carbon atom (cyanide species) as a result, leaving the cyanide species with no lone pairs in the carbon atom and one lone pair in the nitrogen atom. There are no lone pairs of electrons on the carbon central atom that resists the bond pairs of the H-CN bond. According to VSEPR theory, the H-CN bond pairs polarity lead the HCN molecule to take on the linear geometry structure.

The HCN molecule’s one H-CN bond is arranged in asymmetrical polarity order around the linear molecular geometry, giving rise to the HCN molecular shape. The HCN molecule has a linear molecular geometry because there is an electrical repulsion between the lone pairs of electrons in cyanide species and one single bond pair(H-CN) of the HCN molecule.

Lewis structure of HCN has dot electron representative structure. Valence electrons of atoms undergo orbitals mixing in the chemical reactions, giving new types of molecular species of HCN. The molecule is nothing but a bundle of valence electrons from the atoms. But it is converted to bond pairs and lone pairs in the molecular structure.

Electronegative value Difference Calculation of HCN Molecule:

Cyanide species Electronegative difference in HCN:

The carbon atom has an electronegativity of 2.55, while nitrogen has an electronegativity of 3.04 in the HCN molecule. The difference in electronegativity of carbon and nitrogen can be estimated using the method below.

The electronegative value difference between carbon and nitrogen in HCN molecule
Electronegativity value of carbon= 2.55
Electronegativity value of nitrogen= 3.04
Difference of electronegativity value between carbon and nitrogen in HCN molecule = 3.04 – 2.55 = 0.49
Electronegativity difference between CN triple bond calculation of HCN molecule

carbon and hydrogen Electronegative difference in HCN:

The carbon atom has an electronegativity of 2.55, while hydrogen has an electronegativity of 2.2 in the HCN molecule. The difference in electronegativity of carbon and hydrogen can be estimated using the method below.

The electronegative value difference between carbon and hydrogen in HCN molecule
Electronegativity value of carbon= 2.55
Electronegativity value of hydrogen= 2.20
Difference of electronegativity value between carbon and hydrogen in HCN molecule = 2.55 – 2.20 = 0.35
Electronegativity difference between H-CN bond calculation of HCN molecule

The electronegative difference between carbon and nitrogen is less than 0.5. The electronegative difference between carbon and hydrogen is less than 0.5. This indicated the bond polarity moves near to nonpolar nature. H-CN bond polarity in the HCN molecule is slightly nonpolar in nature. But HCN molecule is polar in nature.

Because of this triple bond in carbon and nitrogen(which pull electrons from hydrogen), the HCN molecule’s H-CN bond becomes polar. The total net dipole moment of the HCN molecule is nonzero due to the cancellation of the bond dipole moment in the linear geometry due to the presence of one lone pair of electron on nitrogen and a triple bond between carbon-nitrogen. The electronegativity of an atom is the strength with which it may attract bound electron pairs to its side. The polarity of similar molecules is discussed in our previous post.

As a result, the H-CN bond’s dipole moment is higher due to the polarization of the triple bonds and one lone pair of electrons on the nitrogen atom of cyanide species, and all H-CN bonds’ dipoles are arranged in the asymmetrical HCN molecular geometry. The HCN molecule has a nonzero net dipole moment.

The electron dot structure of the HCN molecule is also known as the HCN Lewis structure. It determines the number of outermost valence electrons as well as the electrons engaged in the HCN molecule’s bond formation. The outermost valence electrons of the HCN molecule must be understood while constructing the Lewis structure of the molecule.

The carbon atom of cyanide species is the middle element in HCN molecular geometry, with four electrons in its outermost valence electron shell and five electrons in nitrogen, whereas the hydrogen atom has one electron in its outermost valence electron shell. Three electrons from carbon and three electrons from nitrogen form a triple bond. The hydrogen atom has one valence electron.

The HCN has a total of 10 valence electrons as a result of the foregoing above-said reasoning. With the core central carbon atom, the one terminal with one hydrogen atom form covalent bonds and another terminal with nitrogen, leaving the nitrogen atom with one lone pair in the terminal of linear molecular geometry.

Because one lone pair on the terminal nitrogen atom create interaction with H-CN bond pairs(but it is negligible in the ground state of the HCN molecule). The bond angle of the H-CN bond in the linear molecular geometry is approximately 180 degrees. This angle is greater than the CH4 molecule bond angle. The H-CN bond length(carbon and nitrogen) is 144pm(picometer).

To sketch the HCN Lewis structure by following these instructions:

Step-1: HCN Lewis dot Structure by counting valence electrons on the carbon and nitrogen atom

To calculate the valence electron of each atom in HCN, look for its periodic group from the periodic table. The carbon, nitrogen, and hydrogen group families, which are the 17th and 1st groups in the periodic table, are both made up of carbon, nitrogen, and hydrogen atoms respectively. In their outermost shells, hydrogen and cyanide species have one and nine valence electrons respectively.

Calculate the total number of valence electrons in the HCN molecule’s outermost valence shell. The first step is to determine how many electrons are in the HCN Lewis structure’s outermost valence shell. An electron in an atom’s outermost shell is known as a valence electron. It is represented by dots in the HCN Lewis diagram. The HCN molecule’s core carbon atom can be represented as follows:

Total outermost valence shell electron of carbon atom in HCN= 4
Total outermost valence shell electron of nitrogen atom in HCN= 5
Total outermost valence shell electron of hydrogen atom in HCN= 1
The HCN molecule has one central carbon, one nitrogen and one hydrogen atoms. Then the total outermost valence shell electrons can be calculated as follows
∴ Total outermost valence shell electrons available for HCN Lewis structure( dot structure) = 1+4+5= 10 valence electrons in HCN.
calculation of total valence electron of HCN molecule

Choose the atom with the least electronegative value atom and insert it in the center of the molecular geometry of HCN. But carbon atom placed in the center of the molecular geometry. We’ll choose the least electronegative value atom in the HCN molecule to place in the center of the HCN Lewis structure diagram in this phase.

But in this case, hydrogen is the least electronegative than carbon and nitrogen. Hydrogen takes a maximum of two-electron in its orbital. This gives hydride ion(H-). So that carbon stays in the central molecular structure. The electronegativity value in periodic groups grows from left to right in the periodic table and drops from top to bottom.

The first step is to put seven valence electrons around the carbon and nitrogen atoms as given in the figure.

Step-2: Lewis Structure of HCN for counting valence electrons around the terminal hydrogen atoms

As a result, carbon is the first atom in the periodic table’s carbon family group. Hydrogen is the first member of the hydrogen family. It is the first element in the periodic table. The electronegative value of the carbon atom is higher than that of the hydrogen atom in the HCN molecule. Furthermore, hydrogen has a one-electron limit since it is the less electronegative element in the HCN molecule.

In the HCN Lewis structure diagram, the carbon atom can be the center atom of the molecule. As a result, central carbon in the HCN Lewis structure, with one hydrogen atom arranged in a linear or tetrahedral geometry.

Add valence electron around the hydrogen atom, as given in the figure.

Step-3: Lewis dot Structure for HCN generated from step-1 and step-2

Connect the exterior and core central carbon atom of the HCN molecule with one single H-CN bond. In this stage, use one hydrogen atom on the outside of the HCN molecule to the central carbon atom in the middle.

Count how many electrons from the outermost valence shell have been used in the HCN structure so far. H-CN single bond carries two electrons because the carbon atom is connected to one hydrogen atom by H-CN single bonds. Bond pairings of H-CN are what they’re called.

So, out of the total of 10 valence electrons available for the HCN Lewis structure, we used four electrons for the HCN molecule’s one H-CN single bond. The HCN molecule has one lone pairs of electrons in the terminal nitrogen atom and no lone pair on carbon atom.

Place the valence electrons in the H-CN bond pair starting with the core carbon, one hydrogen atom in one terminal and one nitrogen atom at another terminal of the HCN molecule. In the HCN Lewis structure diagram, we always begin by introducing valence electrons from the central carbon and nitrogen atom(in step1). As a result, wrap around the central carbon and nitrogen atom’s bond pair valence electrons first (see figure for step1).

The carbon atom in the molecule gets only 8 electrons around its molecular structure. This central carbon atom is octet stable. But it has no lone pairs of electron.

Hydrogen molecule(H2) is in the gaseous state at normal temperature and pressure. It is used as a hydrogenating agent in the field of organic chemistry. It is highly flammable in nature. It is applied in fuel cells. During the combustion, hydrogen gas gives the stream as the final product. This reduces environmental pollution.

Carbon requires 8 electrons in its outermost valence shell to complete the molecular octet stability, two electrons bond pairs in one H-CN single bond, and no lone pairs in the central carbon atom. No lone pairs of electrons on the hydrogen atoms of the HCN molecule are placed in a linear molecular geometry. Carbon already shares 8 electrons to the one H-CN single bonds. Then place the valence electron in the hydrogen atoms, it placed around one electron on hydrogen atom(step-2). There are no valence electrons placed around one hydrogen atom as lone pair of electron.

We’ve positioned 8 electrons around the one-terminal nitrogen atoms(step-3), which is represented by a dot, in the HCN molecular structure above. The carbon atom completes its molecular octet stability in the HCN molecule because it possesses 2 electrons in its (one H-CN single bonds) bond pairs and six electrons(carbon and nitrogen atom) with one hydrogen in the outermost valence shell.

Count how many outermost valence shell electrons have been used so far using the HCN Lewis structure. One electron bond pairs are shown as dots in the HCN chemical structure, whereas one single bond contains two electrons. The outermost valence shell electrons of the HCN molecule(bond pairs) are 2 as a result of the calculation. The total valence electron in a carbon atom is 8.

So far, we’ve used 8 of the HCN Lewis structure’s total 8 outermost valence shell electrons. One lone pair of electron on the terminal nitrogen atom in the linear geometry of the HCN molecule.

Complete the middle HCN atom stability and, if necessary, apply a covalent bond. The central carbon atom undergoes octet stability(due to one single bond pairs of electrons).

The core atom in the HCN Lewis structure is carbon, which is bonded to the one hydrogen atom by single bonds (one H-CN). With the help of one single bond, it already shares 8 electrons. As a result, the carbon follows the octet rule and has 8 electrons surrounding it on the one terminal nitrogen with one lone pair of the HCN molecule’s linear geometry.

How to calculate the formal charge on carbon, nitrogen, and hydrogen atoms in HCN Lewis Structure?

Calculating formal charge on the carbon of HCN molecule:

The formal charge on the HCN molecule’s carbon central atom often corresponds to the actual charge on that carbon central atom. In the following computation, the formal charge will be calculated on the central carbon atom of the HCN Lewis dot structure.

To calculate the formal charge on the central carbon atom of the HCN molecule by using the following formula:
The formal charge on the carbon atom of HCN molecule= (V. E(C)– L.E(C) – 1/2(B.E))
V.E (C) = Valence electron in a carbon atom of HCN molecule
L.E(C) = Lone pairs of an electron in the carbon atom of the HCN molecule.
B.E = Bond pair electron in C atom of HCN molecule
calculation of formal charge on carbon atom in HCN molecule

The carbon core atom (one single bond connected to one hydrogen atom) of the HCN molecule has four valence electrons, no lone pair of electron(zero electrons), and 8 bonding pairing valence electrons. Put these values for the carbon atom in the formula above.

Formal charge on carbon atom of HCN molecule = (4- 0-(8/2)) =0

In the Lewis structure of HCN, the formal charge on the central carbon atom is zero.

Calculating formal charge on the nitrogen of HCN molecule:

The formal charge on the HCN molecule’s nitrogen central atom often corresponds to the actual charge on that nitrogen central atom. In the following computation, the formal charge will be calculated on the central nitrogen atom of the HCN Lewis dot structure.

To calculate the formal charge on the central nitrogen atom of the HCN molecule by using the following formula:
The formal charge on the nitrogen atom of HCN molecule= (V. E(N)– L.E(N) – 1/2(B.E))
V.E (N) = Valence electron in a nitrogen atom of HCN molecule
L.E(N) = Lone pairs of an electron in the nitrogen atom of the HCN molecule.
B.E = Bond pair electron in N atom of HCN molecule
calculation of formal charge on nitrogen atom in HCN molecule

The nitrogen terminal atom (triple bond connected to central carbon atom) of the HCN molecule has five valence electrons, one lone pair of electron(two electrons), and 6 bonding pairing valence electrons. Put these values for the terminal nitrogen atom in the formula above.

Formal charge on terminal nitrogen atom of HCN molecule = (5- 2-(6/2)) =0

In the Lewis structure of HCN, the formal charge on the terminal nitrogen atom is zero.

Calculating formal charge on the hydrogen atom of HCN molecule:

The formal charge on the HCN molecule’s hydrogen terminal atoms often corresponds to the actual charge on that hydrogen terminal atoms. In the following computation, the formal charge will be calculated on the terminal hydrogen atom of the HCN Lewis dot structure.

To calculate the formal charge on the terminal hydrogen atom of the HCN molecule by using the following formula:
The formal charge on the hydrogen atom of HCN molecule= (V. E(H)– L.E(H) – 1/2(B.E))
V.E (H) = Valence electron in a hydrogen atom of HCN molecule
L.E(H) = Lone pairs of an electron in the hydrogen atom of the HCN molecule.
B.E = Bond pair electron in H atom of HCN molecule
calculation of formal charge on hydrogen atom in HCN molecule

The hydrogen terminal atoms of the HCN molecule have one valence electron, no lone pairs of electrons(zero electrons), and two bonding pairing valence electrons(single bond). Put these values for the hydrogen atom in the formula above.

Formal charge on hydrogen atom of HCN molecule = (1- 0-(2/2)) =0

In the Lewis structure of HCN, the formal charge on the terminal hydrogen atom is zero.

Summary:

In this post, we discussed the method to construct the HCN Lewis structure. First, the valence electrons are placed around the carbon and nitrogen atoms. Second, place the valence electron on the hydrogen atoms. Finally, when we combined the first and second steps. It gives HCN Lewis structure. Need to remember that, if you follow the above-said method, you can construct molecular dot structure very easily.