Which of the following is the correct lewis formula for methane (ch4)?

Methane is one of the simple organic molecules, given its straightforward structure. It has the chemical formula of CH4 and comprises one carbon atom forming bonds with four hydrogen atoms. The compound is one of the main constituents of natural gas. It is also known as an alkane. Talking about its properties, Methane is a colorless and flammable gas. It is formed by the decaying of natural minerals and is widely used as fuel. CH4 is also used in the natural production of several organic compounds.

In this blog post, we will find the Lewis Structure, Molecular Geometry, and Shape of the molecule. But before proceeding with the Lewis Dot Structure, we will first look at the total number of valence electrons for this molecule as these are the ones that participate in the bond formation.

CH4 Valence electrons

The electrons that participate in the bond formation and are in the outermost shell of the atom are referred to as valence electrons. 

Total number of valence electrons for CH4 – Valence electrons of Carbon + Valence electrons of Hydrogen

Carbon has four valence electrons.

Each Hydrogen atom has one valence electron, so there are a total of four valence electrons for all Hydrogen atoms.

Total number of valence electrons for CH4 – 4 + 4

= 8

Thus there eight valence electrons for Methane.

CH4 Lewis Structure

Lewis structure is the pictorial representation of the arrangement of valence shell electrons in the molecule, which helps us understand the atoms’ bond formations. The electrons that participate in bond formation are called the bonding pair of electrons, while those that don’t are known as nonbonding pairs of electrons. Lewis structure is also referred to as electron dot structure.

Dots are represented to show the electrons, and lines are used to indicate the bonds between the atoms. Lewis structures are based on the octet rule, which says an atom must have eight valence electrons in its outer shell to attain a structure similar to the closest noble gas. However, many elements are exceptions to this rule.

Let us look at the Lewis Structure of CH4 and determine how the atoms are arranged in the molecule.

Carbon in Methane takes the central position as it is less electronegative than the Hydrogen atoms. Arrange all the Hydrogen atoms around the Carbon atom.

Now each Hydrogen just needs one more valence electron to attain a stable structure. So for doing that, it will share one valence electron of the Carbon atom.

As Carbon has four valence electrons, it will share all four electrons with the Hydrogen atoms. Each bond requires two valence electrons, and hence eight valence electrons are used up by forming bonds.

So in the Lewis structure of CH4 or Methane, there are four single or covalent bonds between each Hydrogen and Carbon atom. There are four bonding pairs of electrons and no lone pair of electrons in this molecule.

CH4 Hybridization

For the CH4 molecule, we will find the Carbon atom’s hybridization as it is the one sharing electrons with Hydrogen atoms and forming bonds. So for finding out the hybridization for the Carbon atom, we will find out the Steric Number.

Steric Number- Number of atoms attached to the central atom + number of lone pairs on the atom

= 4+0

= 4

Hence four hybrid orbitals are formed for CH4, and referring to the table given below, we can say that it has sp3 hybridization. One 2s orbital and three 2p orbitals are hybridized for the Carbon atom.

CH4 Molecular Geometry

Molecular geometry helps us understand the arrangement of atoms in 3D for any given molecule. For the Methane molecule, there are four covalent bonds between Hydrogen and Carbon atoms. The molecule has quite a symmetry in its arrangement as there are bonds on all four sides of the central atom.

According to VSEPR theory, electron pairs of the same nature repel each other. There are four bonding pairs of electrons, so to keep their repulsive forces at a minimum, they take the tetrahedral molecular geometry.

Hence, CH4 or Methane has a Tetrahedral Molecular geometry.

CH4 Bond Angles

One can use AXN Notation to find out the molecular geometry and the bond angles for any molecule. Here CH4 follows the AX4 notation, and hence according to the table given below, the bond angles are 109.5°

The CH4 molecule will have 109.5° bond angles as there is no distortion in its shape. Generally, the lone pairs in the molecule distort the shape of the molecule, which changes the molecule’s bond angles. But as there are no lone pairs of electrons in this molecule, H-C-H’s bond angle is 109.5°.

CH4 Shape

Methane has a tetrahedral molecular geometry, and thus, it is a tetrahedral shape molecule.

Concluding Remarks

To summarize this blog, we can conclude the following points for the Methane molecule:

• CH4 molecule is made up of one Carbon atom and four hydrogen atoms.
• There are four single bonds in the molecule between Carbon and Hydrogen atoms.
• A total of 8 valence electrons are there for this molecule.
• All the valence electrons are used up in the bond formation; hence the molecule has no lone pairs, and there are four bonding pairs of electrons. 
• Carbon has sp3 hybridization, and the molecule takes up a tetrahedral shape to keep the repulsive forces of bonding pairs at a minimum.
• The bond angle of H-C-H is 109.5°. 

To know about the polarity of the CH4 molecule, check out our detailed blog post on CH4polarity to find out if the molecule is polar or nonpolar. 

Methane or CH4 is a naturally occurring gas and relatively abundant on the Earth, making it an economically efficient fuel. As it releases more light and heat on burning, it is preferred more than coal, fossil fuel, or gasoline for energy production.

It is one reason why overproduction of methane has made it a considerate greenhouse gas (GHG) where it is affecting the temperature and climate system of the Earth.

The Lewis structure is a pictorial representation of how many valence electrons are present in an atom.

Moreover, the diagram also helps with determining how the bond formation is taking place between the atoms to form a molecule, ultimately a compound.

The Lewis diagram is drawn by showing valence electrons in the form of dots drawn around the atom and lines predicting the bond formation.

These lines also determine whether a single, double, or triple bond has been formed helping with predicting the hybridization of the central atom.

Valence Electrons

Valence electrons are those electrons that take participation in the bond formation and exist in the outermost shell of an atom.

These are the electrons that participate in the bond formation by either getting donated or accepted between the atoms.

There can be a maximum of eight valence electrons in an atom.

To know the number of valence electrons in a carbon atom, first, it is crucial to find its atomic number which is six. So, the electronic configuration of the carbon will be 1s2 2s2 2p2.

As the p shell needs to accommodate a total of six electrons, there is a dearth of four electrons. Due to this, the number of valence electrons in the carbon atom has been four.

Whereas, on the other hand, the atomic number of the hydrogen atom is one that makes its electronic configuration 1s1.

As there is a dearth of only one electron, the number of valence electrons in a hydrogen atom is one.

Octet Rule

This rule says the maximum valence electrons that can be drawn around an atom are eight.

If we follow this rule, it is much easier to see that carbon has a dearth of four valence electrons whereas, hydrogen needs only one valence electron.

The lewis structure of CH4 is drawn to fulfill the need of valence electrons by all the atoms.

Lewis Structure of CH4

The lewis structure of carbon and hydrogen atom says- to form a single CH4 molecule, a total of eight valence electrons participate in the shared bonding to fulfill the need of eight more valence electrons.

Here we will learn about how the lewis dot structure is drawn for CH4 molecule, step by step.

Firstly, look for the total number of valence electrons required by a single CH4 molecule, which is sixteen.

Next, a search of electrons is required by a single CH4 molecule to reach a stable condition.

It is eight for a single CH4 molecule, as four are needed by the carbon atom and one by hydrogen atom each.

The next step is to find the total number and type of bond-forming that atoms within a single CH4 molecule.

A single shared covalent bond is formed between each carbon and hydrogen atom (C-H).

Lastly, search for the central atom that is usually the single atom in a molecule. It is carbon in the case of methane (CH4).

Now, draw the lewis structure of the methane (CH4) as below

The Geometrical Structure of Methane (CH4)

The single-molecule of methane (CH4) is tetrahedral with no lone pairs on any atom. This behavior is explained with the help of the Valence Shell Electron Pair Repulsion (VSEPR) theory.

This theory is used to predict the geometrical structure of a molecule along with the reason for such a shape.

For the methane (CH4) molecule, this theory says as there exists no distortion in the structure of CH4, it is an ideal bent-shaped molecule or tetrahedron having a bond angle of 109.5° between hydrogen-carbon-hydrogen atoms (H-C-H).

Due to the symmetrical shape of the bonds formed in the CH4 molecule, the charges on its atoms are equally distributed and no polarization takes place ie; the Methane molecule is a nonpolar molecule.

For better understanding, you can refer to the article written on the polarity of CH4.

The distortion from the ideal bond angle within a molecule occurs because of the presence of lone pairs and bond length between the central atom and the side atoms.

From the Lewis structure, it can be understood that an equal number of electron sharing is taking place between the carbon atom and four hydrogen atoms altogether.

It is the reason why the structure of methane is highly stable in nature.

Hybridization in Methane (CH4)

Hybridization is a mathematical process of mixing and overlapping at least two atomic orbitals within the same atom to produce completely different orbitals and the same energy called new hybrid orbitals.

If we look for the hybridization of the carbon atom in the methane (CH4), it is sp3.

It is due to the reason that the one 2s and three 2p orbitals of the carbon mixes and overlaps to form four new hybrid orbitals of equal energy and similar shape.

Moreover, the new four sp3 hybrid orbitals have 25% characteristics of s orbital whereas 75% characteristics of p orbital.

In addition to this, the four hydrogen atoms also use these four new hybrid orbitals to produce carbon-hydrogen (C-H) sigma bonds.

We know that there exists one sigma bond (σ) and no pi (π) bond in the single shared covalent bond.

So, this is how four sigma bonds are formed in a methane molecule with no pi bond where the sigma bond further contributes to the hybridization of the carbon atom.

Also, check out a related article on the CH4 Intermolecular Forces.

Molecular Orbital diagram of CH4

The molecular orbital diagram helps with determining how mixing and overlapping have taken place in a molecule to conclude upon the hybridization type.

As per the figure, the four sp3 hybrid orbitals of the carbon mixes and overlaps with four 1s atomic orbitals of the hydrogen.

Each carbon and hydrogen bond (C-H) forms due to head-on overlapping of the only occupied sp3 hybrid orbital of the carbon with the 1s orbital of the hydrogen.

It can be confirmed from the fact that only sigma bonds undergo head-on overlapping whereas pi bonds undergo lateral overlapping.

As there exist no pi bonds, only head-on overlapping takes place within the methane (CH4) molecule.

From the diagram, you can see that all the four orbitals at the top are empty having a change in phase between carbon and hydrogen.

To put an electron in any of these orbitals, the bonding energy needs to be reduced between the bonded carbon and hydrogen atoms.

On the other hand, all four orbitals at the bottom are filled as they are lower in energy than the non-bonding energy level.

The molecular orbital of the lowest energy is equally distributed throughout the molecule.

Conclusion

The Lewis structure of the methane (CH4) molecule is drawn with four single shared covalent bonds between the carbon and hydrogen atoms each.

Moreover, as there exist sigma bonds only and one 2s and three 2p orbitals of the carbon produce four new hybrid orbitals, the hybridization of CH4 is sp3.

It is interesting to realize that irrespective of having sigma bonds, the new hybrid orbitals acquire major characteristics of p orbital.

Moreover, the bond angle is the ideal tetrahedral angle of 109.5° because of no lone pair of electrons on an atom.