CH3F Molecular Geometry

CH3F Lewis Structure, Molecular Geometry, Hybridization

CH3F Molecular Geometry

CH3F (Fluoromethane) is made of one carbon, three hydrogens, and one fluorine atom. It is also known as methyl fluoride, Freon 41, Halocarbon-41, and HFC-41. Fluoromethane is the result of one fluorine atom substituted with one carbon from CH4 (methane).

It is a non-toxic, liquefiable, and flammable gas at standard temperature and pressure. Fluoromethane is mainly used as an etching gas for the manufacturing processes of semiconductors.

Properties of Fluoromethane (CH3F)

  • It is a colorless, non-toxic, flammable, and liquefiable gas at STP.
  • CH3F has a pleasant odor like ether at higher concentrations.
  • CH3F molar mass is 34.03 g/mol and density is 1.4397 g/L at saturation.
  • Its melting and boiling points are -137.8 C and -78.4 C respectively.
  • The solubility of CH3F in water is 1.66 L/kg (2.295 g/L).
Molecule Name Fluoromethane
Chemical Formula CH3F
Total valence electrons of CH3F 14
Formal charges in CH3F 0 (Zero)
Molecular geometry of CH3F Tetrahedral
Electron geometry of CH3F Tetrahedral
Bond Angle of CH3F 109.5
Dipole moment of CH3F 0 (Zero)
Hybridization of CH3F Sp3
CH3F Polar or nonpolar? Polar

Here in this article, we will know the step-to-step processes of drawing the Lewis dot structure of CH3F along with its molecular geometry, shape, electron geometry, Molecular Orbital/ MO diagram, hybridization, and more.

CH3F (Fluoromethane) Lewis Structure

Lewis structure is a very simplified representation of valence shell electrons in a chemical species like an atom, ion, or molecule. It indicates how electrons are situated around the atoms either as lone pairs, or bonds (covalent, coordinate bonds). In Lewis structure, dots represent lone pairs of electrons while lines indicate bond pairs of electrons.

Fluoromethane is made of one carbon, three hydrogens, and one fluorine atom. Carbon has the least electronegativity compared to fluorine and hydrogen as it holds a central position.

Before drawing the Lewis structure, you must have some basic ideas about valence electrons, the octet rule, and formal charge for a better understanding.

What are the Valence Electrons?

Valence electrons can be defined as the electrons present in the outermost shell of an atom that can take part in chemical bond formation either by transferring to or sharing with another atom. For example, hydrogen has only one electron in its outermost shell, which means hydrogen has only one valence electron that can take part in chemical bonding. While carbon has a total of four electrons in its outermost shell, it means carbon has a total of 4 valence electrons which can take part in bonding.

What is the Octet Rule?

The octet rule can be defined as the tendency of an atom to have eight electrons in its outermost shell (except H and He). In octet rule atoms gain, lose, or share electrons to attain their nearest inert/noble gas configuration in the outermost shell.

What is the Formal charge?

The formal charge (FC) can be defined as the difference between the actual number of valence electrons of each atom and the number of electrons the atom is associated with. The formal charge of any molecule can be easily calculated with the following formula,

Formal Charge (FC) = [V – N – B/2] where,

V = total number of valence electrons

N = total number of nonbonding valence electrons

B = total number of electrons shared in bonds

Steps for drawing Lewis dot structure of CH3F

Step 1. Count the total number of valence electrons present on each atom of the CH3F molecule.

CH3F molecule has a total of 14 electrons which is simply an addition of one carbon, three hydrogen, and one fluorine valence electrons.

The valence electron of hydrogen is 1, as hydrogen lies in the first group.

Similarly, carbon has a total of 4 valence electrons as it lies in the 14th group of the periodic table.

And fluorine has a total of 7 valence electrons as it is in the 17th group of the periodic table.

Now to calculate the total number of valence electrons present in the CH3F molecule, we must have to add each individual atom’s valence electrons. It means, CH3F has a total of 4 + 3*1 + 7 = 14 valence electrons.

Step 2. Determine the total number of valence electrons pairs for the CH3F molecule.

The total number of valence electrons pairs for a molecule is equal to the addition of sigma bonds, pi bonds, and lone pairs present at the valence shells. But we can easily calculate it by just dividing the total number of valence electrons by two which will give the valence electrons pairs.

In CH3F, the total number of valence electrons is 14. So, the valence electrons pairs will be 14/2 = 7.

Step 3. Identify the Central atom and draw a simple skeleton diagram.

Choosing the central atom while drawing the Lewis structure is the trickiest part. For choosing a central atom, we must have to consider the number of atoms and the electronegativity of the atom. The atom having a lower electronegativity value will be the central atom.

CH3F Molecular Geometry

In CH3F, the carbon atom (C= 2.55 ) has a lower electronegativity value than fluorine (F= 3.98 ) that’s why carbon acquires the central position as hydrogen never can be the central atom.

Step 4. Put lone pairs of electrons on each atom.

Now Time to put lone pair of electrons on atoms. Starting with outer atoms must have 8 electrons (except H and He) to fulfill octet.

CH3F Lewis Structure

We have a total of seven electrons pairs (calculated in step 2). Place one-one electrons pair to each hydrogen and four electron pairs (8 valence electrons) to fluorine. Still, we have two electron pairs left which will be placed on carbon atoms. Now we have used all 7 lone pairs of electrons (3 lone pairs to H, 4 lone pairs to F, and 2 lone pairs to C).

Step 5. Complete the octet of all the atoms and make a covalent bond if necessary.

Now time to check the octet for all the atoms in CH3F. Starting with outer atoms, each hydrogen atom has two electrons which fulfill their duplet as their outer shell is full. Similarly, fluorine has also 8 electrons which means fluorine also has octet completed.

But central carbon atom has only four electrons, four more electrons will be required for carbon to full outermost shell. The carbon atom is not obeying the octet rule yet so the carbon atom will share one electrons pair to hydrogen and fluorine. As you can see central carbon atom has also a total of 8 electrons which complete its octet. Now all the atoms have completed their octet (outermost shell full) by forming four single covalent bonds.

CH3F Lewis Structure
CH3F Lewis Structure

Step 6. Calculate the formal charge distribution on all atoms and check the stability.

Now we have to calculate the formal charge distribution of all atoms to check the stability of the molecule.

The formal charge of an atom can be calculated as,

Formal charge (F.C) = [Valence electrons (V) – Lone pair of electrons (L) – Bond pair of electrons (B)/2]

We have three different atoms in CH3F molecules so calculate their formal charge separately,

  1. Formal charge distribution on H = 1 – 0 – 2/2 = 0
  2. Formal charge distribution on C = 4 – 0 – 8/2 = 0
  3. Formal charge distribution on F = 7 – 6 – 2/2 = 0

All the atoms in the above structure have completed octet rules comfortably and there is not any formal charge distribution on any atom. That’s why the above structure is the best stable Lewis dot structure of the CH3F molecule.

CH3F Molecular Geometry & Shape

CH3F molecule has a tetrahedral geometry. There are a total of four covalent bonds with central carbon atom, three C – H bonds, and one C – F bond. There are not any lone pairs present on the central carbon atom. The structure of CH3F is similar to CH4 but the only bond angle differs as fluorine has a higher electronegativity.

CH3F Molecular Geometry

We can also determine CH3F molecular geometry and shape according to VSEPR (Valence Shell Pair Repulsion) theory. For that, we have to use the AXN method.

AXN notation for CH3F molecule:

  • A is the representation for the central atom, so, in CH3F, C is the central atom which means A = Carbon
  • X represents the number of bonded atoms with the central atom, i.e., carbon is bonded with 4 atoms (three hydrogens and one fluorine). Therefore, X = 4
  • N represents the total number of lone pairs of electrons present on the central atom. But there is no lone pair of electrons present on the central carbon atom so that N = 0

Now the generic AXN formula for the CH3F molecule will be AX4N0 or AX4.

According to VSEPR theory, if the molecule has a generic formula AX4 then its molecular geometry and electron geometry will be tetrahedral.

CH3F Molecular Geometry VSEPR

CH3F Hybridization

Fluoromethane (CH3F) has an sp3 hybridization as it has four sigma bonds and no lone pair of electrons on the central atom. The steric number comes out 4 which indicates sp3 hybridization.

We can also determine the hybridization of molecule via following steps as given below:

  • If the total number of valence electrons is less or equal to 8, divided by 2.  (V.E. < 8 divided by 2)
  • If the total number of valence electrons of a molecule is between 8 to 56, divide it by 8. (8 < V.E. < 56 divided by 8)
  • Similarly, if the valence electrons of a given molecule is more than 56, divided by 18. (V.E. > 56 divided by 18)

In our case, CH3F has a total of 14 valence electrons so it will be divided by 8 (i.e., 14 / 8)

As a result, we get 6 remainder and 1 quotient so again divide 6 with 2 and we get 3 quotient and zero remainder.

Here we get a total of 1 + 3 = 4 orbitals which means CH3F molecule has sp3 hybridization. Similarly, carbon and fluorine have also sp3 hybridization and as we know hydrogen is unable to hybridize so leave it unusual.

 

CH3F MO Diagram

CH3F Molecular Orbital (MO) Diagram

 

Summary

 

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