CH2F2 Lewis structure is made up of one carbon (C) atom, two hydrogens (H), and two fluorine (F) atoms. The carbon (C) atom is kept at the central position and other atoms are at the surrounding position. The lewis structure of CH2F2 contains 4 single bonds in the form of two C-H bonds and two C-F bonds.
The drawing process of the CH2F2 lewis structure is easy and simple. Let’s see how to do it.
Follow some steps for drawing the Lewis dot structure for CH2F2
1. Count total valence electron in CH2F2
In the very first step, we will count the total valence electron in the CH2F2 molecule. To calculate the valence electron, look at the periodic group of the individual atoms – carbon, hydrogen, and fluorine.
The fluorine atom belongs to the periodic group 7A or 17th in the periodic table, hence, the valence electron for the fluorine atom is 7.
The carbon atom is situated in the 14 or 4A periodic group, hence, its valence electron is 4. The hydrogen atom has only one valence electron.
∴ Total number of valence electrons available for the CH2F2 Lewis structure = 4 + 1(2) + 7(2) = 20 valence electrons [∴ CH2F2 molecule has one carbon, two hydrogen, and two fluorine atoms]
2. Find the least electronegative atom and place it at center
Now we will find the least electronegative atom in the CH2F2 compound, after that, we will place it at the center of the lewis diagram and the rest atoms will be spread around it.
The electronegativity value of the carbon atom is 2.55, for a fluorine atom, it is 3.98.
“Hydrogen atoms always go on the outside of a Lewis Structure”.
Hence, the carbon atom is the least electronegative atom in the CH2F2 compound, therefore, we will put the carbon atom in a central position and (the fluorine and hydrogen atoms) in the surrounding position in the lewis diagram.
3. Connect outer atoms to the central atom with a single bond
In this step, we simply connect each outer atom(fluorine and hydrogen) to the central atom(carbon) with the help of a single bond.
Now count the valence electron used in the above structure. A single bond means two electrons, in the above structure, four single bonds are used for connecting the two fluorine and two hydrogens atoms to the carbon central atom.
Therefore, (4 single bonds × 2) = 8 valence electrons are used in the above structure from the total of 20 valence electrons available for drawing the lewis structure of CH2F2.
∴ (20 – 8) = 12 valence electrons
So, we are left with 12 valence electrons.
4. Place remaining electrons on outer atoms and complete their octet
In this step, we will put the remaining valence electron on the outer atom first for completing their octet. In a CH2F2 molecule, the outer atom is hydrogen and fluorine.
⇒ Hydrogen atoms only need two valence electrons to fulfill the outer shell.
⇒ A fluorine atom needs 8 electrons to complete the outer shell.
As you see in the above figure, we have placed the 6 electrons represented as dots around both fluorine atoms.
∴ Fluorine atoms completed their octet since they have 8 electrons(6 electrons represented as dots + 2 electrons in a single bond).
∴ Hydrogen atoms already completed their octet since they are joined with one single bond means 2 electrons and remember, hydrogen only needs 2 electrons to have a full outer shell.
Now once again count the total valence electron in the above structure.
(4 single bond × 2 electrons + 12 electrons represented as dots) = 20 valence electrons are used in the above structure.
Remember, we had a total of 20 valence electrons available for drawing the lewis structure of CH2F2, and in the above structure, we used all valence electrons.
Also, the Carbon central atom has completed its octet as well since it has connected with 4 single bonds(8 electrons).
Now just check the formal charge for the above structure to know whether it is stable or not.
5. Check the stability with the help of a formal charge concept
The lesser the formal charge on atoms, the better the stability of the lewis diagram.
To calculate the formal charge on an atom. Use the formula given below-
⇒ Bonding electrons around carbon (4 single bonds) = 8
∴ (4 – 0 – 8/2) = 0 formal charge on the carbon central atom.
So, all atoms in the above structure get a formal charge equal to zero, hence, this is our most stable and appropriate lewis dot structure of Difluoromethane (CH2F2).
The molecular geometry or shape of CH2F2 is tetrahedral. The central atom Carbon (C) is bonded with four atoms (two hydrogen and two fluorine atoms) and it has no lone pair which means, it is an AX4 type molecule, as per VSEPR theory, its geometry or shape is tetrahedral.
A represent central atom
X represent the number of bonded atom to central atom
According to VSEPR theory or chart, the AX4 type molecule forms tetrahedral molecular geometry or shape.
It should be noted that, In CH2F2, the carbon (C) atom has attached to four bonded atoms(2 hydrogen and 2 fluorine atoms), and it contains no lone pair which means, there are four regions of electron density around the carbon central atom.
When there is no lone pair, then, central atom with four region of electron density adopt a tetrahedral structure because repulsion is minimum in electron pairs at this position.
So, we can say, the molecular geometry or shape for CH2F2 is tetrahedral and its electron geometry is also tetrahedral since all are bonding regions around the central atom with no lone pair.
Hybridization of CH2F2
We can calculate the hybridization of CH2F2 using the steric number formula given below:
Steric number = (Number of bonded atoms attached to central atom + Lone pair on central atom)
∴ Steric number of CH2F2 = (Number of bonded atoms attached to carbon + Lone pair on carbon atom)
As per the CH2F2 lewis structure, the carbon atom is bonded with four atoms(two fluorine and two hydrogens) and contains zero lone pairs.
∴ Steric number of CH2F2 = (4 + 0) = 4
So, for the steric number of 4, we get the hybridization of CH2F2 is Sp3.
The bond angle of CH2F2
According to the VSEPR theory, for a regular tetrahedral structure, the bonded atoms around the central atom will spread at an angle of approx 109.5° to minimize the repulsion and attains stability.
The approx bond angle in CH2F2 is based on the type of bond, ∠F-C-H = 109º, ∠H-C-H = 113º, ∠F-C-F = 108.5º. [Check source]
Is CH2F2 polar or non-polar? CH2F2 is a polar molecule. The bond present in this molecule, C-F are polar since there is a large electronegativity difference between them.
The electronegativity of Carbon = 2.55
The electronegativity of Fluorine = 3.98
∴ The difference in electronegativity of Fluorine and Carbon = 1.40
The fluorine is more electronegative than carbon, hence, it will attract a negative charge and carbon will get a positive charge. The separation of charge between them leads to dipole moment directed from Carbon to Fluorine.
However, the molecule (CH2F2) has a symmetrical shape i.e. Tetrahedral. Still, the dipole moment of the C-F bond will not cancel out because the C-H bonds are almost nonpolar, hence, the weak dipole of C-H bonds is unable to cancel out the strong dipole of C-F.
It results in some permanent dipole moment in the molecule which is 1.97 D. Therefore, we can say, the overall CH2F2 molecule is polar in nature.
How many bonding pairs and lone pairs are present in the lewis structure of CH2F2?
Bonding pairs are the pair of electrons that are in a bond. A single bond has one bond pair means 2 bonding electrons.
Lone pairs are those represented as dots in the lewis diagram that do not take part in the formation of bonds and are also called nonbonding electrons.
By looking at the CH2F2 lewis structure, we see there are 4 single bonds means 4 bonding pairs, and there are 12 dots electrons means 6 lone pairs. [∴ 2 dot electrons means one lone pair).
So, in the CH2F2 lewis structure, there are 6 lone pairs and 4 bonding pairs present.
How many valence electrons are present in the CH2F2 lewis structure?
⇒ Valence electron in hydrogen atom = 1
⇒ Valence electron in fluorine atom = 7
⇒ Valence electron in carbon atom = 4
∴ Total number of valence electrons available for the CH2F2 Lewis structure = 4 + 1(2) + 7(2) = 20 valence electrons
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
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