MO Diagram, C2H4 Lewis Structure, Molecular Geometry, and Hybridization

Hydrocarbons are an indispensable and inseparable component of chemistry. The majority of hydrocarbons are found naturally in these fossil fuels, be they petroleum, crude oil, or natural gas. Additionally, they can be found in synthetic polymers and other man-made plastics.

As the name suggests, they are organic in origin and composed of only carbon and hydrogen. Occasionally, it also produces compounds with additional elements, such as sulphur, nitrogen, etc.

Even though these are among of the simplest organic compounds we might encounter, their physical and chemical properties vary considerably.

Ethylene/Ethene

This article will discuss ethylene, one of the most prevalent and commonly utilised hydrocarbons (C2H4).

Do you realise this substance is even lighter than air?

C2H4 is a simple straight-chain hydrocarbon with a sweet odour and a colourless appearance.

We have encountered this chemical whenever we have read about organic chemistry, haven’t we?

Therefore, it is essential that we gain a thorough understanding of C2H4 to better comprehend the nature of straight-chain hydrocarbons.

Chemical Interactions in Hydrocarbons

Carbon has a covalent character when it comes to forming bonds with hydrogen, which results in the development of various types of hydrocarbons.

From the simplest, such as methane and benzene, to the more complex, such as natural rubber, we encounter several HCs in our daily lives.

There are various types of hydrocarbons in organic chemistry, including straight-chain, cyclic, and even branched hydrocarbons.

Straight-chain hydrocarbons are the most basic and easiest to interpret group. Here, we have:

Saturated hydrocarbons have the structure H-(CH2)n and are also known as acyclic straight-chain alkanes. They create solitary bonds by chance. Methane and ethane are examples.

These hydrocarbons create double and triple bonds and are referred to as alkenes and alkynes, respectively. Examples are acetylene and ethylene.

Chemical Interactions in Ethylene

Have you ever pondered the universe’s singularity and immense variety?

How is this entire cosmos composed of several atoms?

Now, atoms do not typically exist in a solitary state; everything we observe around us is primarily composed of atoms that have merged to form molecules.

We obtain molecular compounds based on the nature of atoms and their propensity to attract or repulsion another atom of the same or a different type.

And this process of two or more atoms approaching one another and deciding to remain together is known as chemical bonding.

To gain a thorough understanding of ethylene, it is sufficient to first comprehend its bonding characteristics.

The nature of this carbon-hydrogen bond is covalent. Let’s proceed and discuss this systematically.

Lewis Structure of C2H4

The electron dot structure, also known as the Lewis Structure, is a diagrammatic representation of a molecule that includes the constituent atoms and valence shell electrons.

Before we dive in, we’d like to expose you to (or, if you’re already familiar, refresh you on) some incredibly key ideas that will make your knowledge of ethylene bonding much easier!

Valence electrons

The nucleus of an atom is around by negatively charged electrons, which are present at various levels or shells.

The outermost shell is known as the valence shell, and its electrons are known as valence electrons.

The number of an atom’s valence electrons is comparable to its valency, which in turn defines the atom’s combining capability.

Octet Rule

Please review the periodic table. Observing the final group reveals that all elements are inert gases with eight electrons in their valence shells (except He which has two).

In order to achieve the same valency of eight, the atoms of the major groups tend to acquire extra electrons. This is referred to as the octet rule or octet completion.

Lewis Structure Steps for C2H4

Obtaining the Lewis Structure of any molecule is simple if specific protocols are followed.

Alkene that is unsaturated is C2H4.

Let’s determine how to go with this:

Step 1: Count the number of atoms in an ethylene molecule.

2 Carbon and 4 Hydrogen.

Hydrogen is the first element in the periodic table; hence, it possesses one valence electron.

In the case of carbon, each valence electron has four electrons.

the number of valence electrons in a single C2H4 molecule.

= 24+14 =12.

Step 2: Having determined the total valence number, we can now determine which atom is the least electronegative.

For hydrocarbons, the carbon will always be placed in the centre. Hydrogen atoms will occupy the outermost locations.

Step 3: Now that the atoms have been represented by their symbols, let’s represent the valence electrons with dots.

Here, we can observe that the octet of one carbon atom is complete (the Octet rule has been discussed before). However, the second carbon atom in the centre lacks two electrons.

Therefore, we can take the electrons from the bottom and position them in the middle between the two C atoms.

Step 4: The octet fulfilment idea is complete. As a result of the formation of two bonds, we will have a double bond structure. Hence, C2H4 is an alkene.

Here, we offer the most relevant and suitable Lewis Structure Sketch of ethylene.

Molecular Geometry

C2H4 geometry

When the Lewis Structure of C2H4 is depicted in two dimensions, it is linear. In reality, ethene’s molecular structure is not linear.

Therefore, it is not sufficient to merely sketch a Lewis structure diagram to comprehend chemical bonding. We must also consider molecular geometry.

By offering a three-dimensional image of the molecule, molecular geometry provides a clearer picture of the internal atomic chemistry.

In addition, we are provided with information regarding the bond angle and length.

As we already know, C2H4 is an alkene, or a double-bonded hydrocarbon.

Examine the VSEPR theory that will be utilised to decipher the molecular geometry.

VSEPR

VSEPR refers to the model or theory of Valence Shell Electron Pair Repulsion. Similar charges repel one another. Therefore, negatively charged valence electrons tend to repel one another within a molecule.

The form is explained by the VSEPR theory by minimising the electronic repulsion. Here, we must deal with lone or unshared electron pairs and bound pairs.

For C2H4

In the Lewis structure of C2H4, there are three bound electron pairs and zero lone electron pairs surrounding each carbon.

According to the VSEPR diagram, the ethene molecule has a trigonal planar structure. As depicted in the diagram, two overlapping triangles are present. This is because each carbon is surrounded by a planar triangle.

The angle of the connection is roughly 120 degrees.

C2H4 Hybridization

The process through which atomic orbitals join to generate hybrid orbitals is known as hybridization.

The electrical configuration of the atoms is the most important factor to consider when determining the hybridization of any given molecule.

C: 1s2 2s2 2p2

H: 1s1

One sigma and one pi bonds are present in a double bond. A sigma bond exists in a single bond. Consequently, two sp2 hybrid orbitals, one from each carbon atom, combine to produce a sigma bond in C2H4.

In addition, the unhybridized 2p orbitals (2py or 2pz) of the two carbon atoms unite to form the pi bond. This results in the double bond C=C.

Other sp2 hybrid orbitals generate sigma bonds between C and H, resulting in a single-bonding structure between C and H.

C2H4 Molecular Orbital (MO) Diagram

The molecular orbital theory is a quantum mechanics concept in which atomic particles combine linearly to create molecular orbitals and the wave nature of atomic particles is described.

Here, the bond strength is determined by the degree of overlap, which in turn is determined by the spatial proximity of the combining atoms.

Sigma orbital overlap denotes the conclusion of interactions.

This indicates a side-by-side approach to the planet.

There are three basic types of orbitals: bonding orbitals, nonbonding orbitals, and antibonding orbitals.

If we analyse solely the pi bonds, we can see that the unhybridized 2p orbitals (explained before in the section on hybridization) will now form MO – a bonding orbital and an antibonding orbital.

The bonding orbital will have a larger electron density, which will hold the atoms together by the attraction of the nuclei.

The anti-bonding *orbital will observe a greater electron density distance, hence weakening the connection and creating repulsion.

CC is an abbreviation for Highest Occupied Molecular Orbital (HOMO).

The CC indicates LUMO ( Lowest Unoccupied Molecular Orbital). (the orbital for antibonding stays vacant)

The diagram above depicts the Molecular Orbital (MO) structure of ethene/ethylene.

Molecular polarity of C2H4

The C2H4 molecule is non-polar because all of its atoms are organised symmetrically and both carbon atoms exert the same force on the linked electrons.

Due to the uniform distribution of charges across the molecule, the dipole moment of the molecule is also zero.

For more specific information regarding the polarity of C2H4, please refer to the article on C2H4 polarity.

Below is a video describing the Lewis structure drawing of C2H4. Have a look

Conclusion

Ethene, or C2H4, is a common acyclic alkene with a straight chain and an important organic hydrocarbon. Having a double C=C bond, it is unsaturated, giving rise to a variety of characteristics.

Here, we learned how to draw the correct Lewis Structure and determine the ethylene molecule’s molecular geometry. In addition, we addressed its hybridization and the concept of molecular orbitals.

In summary, we have discussed the bonding properties of ethylene.

We appreciate your reading!

Read more: The pH of Tomatoes – Acidic or Basic?

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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