How to draw CH3Br Lewis Structure? - Science Education and Tutorials

The bromomethane chemical formula is CH3Br. Drawing CH3Br Lewis Structure is very easy to by using the following method. Here in this post, we described step by step method to construct CH3Br Lewis Structure. The carbon, bromine, and hydrogen elements come as the member of the carbon, halogen, and hydrogen family groups from the periodic table respectively. The valence electrons in carbon, bromine, and hydrogen are four, seven, and one respectively. Bromomethane is used as an organic volatile solvent in organic reactions.

Table of Contents

Key Points To Consider When Drawing The CH3Br Structure

A three-step approach for drawing the CH3Br Lewis structure can be used. The first step is to sketch the Lewis structure of the CH3Br molecule, to add valence electron around the carbon atom; the second step is to add valence electrons to the one bromine and three hydrogen atoms, and the final step is to combine the step1 and step2 to get the CH3Br Lewis Structure.

The CH3Br Lewis structure is a diagram that illustrates the number of valence electrons and bond electron pairs in the CH3Br molecule. The geometry of the CH3Br molecule can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory), which states that molecules will choose the CH3Br geometrical shape in which the electrons have from one another.

Finally, you must add their bond polarities to compute the strength of the C-Br bond (dipole moment properties of the CH3Br molecule). The carbon-bromine bonds in bromomethane(CH3Br), for example, are polarised toward the more electronegative bromine and because both bonds have the same size and are located around four terminals with one bromine and three hydrogen atoms, their sum is non zero due to the CH3Br molecule’s bond dipole moment and the lone pairs of electron on one bromine atoms. The CH3Br molecule is classified as a polar molecule.

The molecule of bromomethane (with tetrahedral molecular geometry) is tilted, the bond angles between bromine, carbon, and hydrogen are 111.5 degrees. It has a difference in electronegativity values between carbon and bromine atoms, with carbon’s pull being less than bromine’s terminal in the CH3Br molecule. As a result, it has the permanent dipole moment. The CH3Br molecule has a permanent dipole moment due to an unequal charge distribution of negative and positive charges. The net dipole moment of the CH3Br molecule is 1.82 D.

CH3Br Lewis Structure:

The central atom is carbon, which is bordered on four terminals with one bromine atom, three hydrogen atoms, and no lone pair on the carbon in the tetrahedral geometry. Carbon has four outermost valence electrons, indicating that it possesses four electrons in its outermost shell, whereas bromine only has seven valence electrons in its outermost shell. To complete the octet of the bromine atom, a bromine terminal atom requires one electron. If you’re interested in learning more about the bromine octet rule, please see in our previous post.

One bromine and three hydrogen atoms establish covalent connections with the central carbon atom as a result, leaving the carbon atom with no lone pair. There is no lone pair on the carbon central atom that resist the bond pairs of the one C-Br and three C-H. According to VSEPR theory, no electronic repulsion of the lone pair and bond pair leads the CH3Br molecule to take on a tetrahedral molecular geometry shape.

The CH3Br molecule’s C-Br bonds are arranged in asymmetrical order around the tetrahedral molecular geometry, giving rise to the CH3Br molecular shape. The CH3Br molecule has a tetrahedral molecular geometry because there is no electrical repulsion between lone pair and bond pairs of CH3Br molecule.

Electronegative Difference Calculation of CH3Br Molecule:

Calculating the electronegative difference in carbon and bromine in CH3Br

The carbon atom has an electronegativity of 2.55, while bromine has an electronegativity of 2.96 in the CH3Br molecule. The difference in electronegativity can be estimated using the method below.

The electronegative value difference between carbon and bromine in CH3Br molecule
Electronegativity value of carbon in CH3Br = 2.55
Electronegativity value of bromine in CH3Br= 2.96
Difference of electronegativity value between carbon and bromine in CH3Br molecule= 2.96 – 2.55 = 0.41
Electronegativity difference between C-Br bond calculation of CH3Br molecule

The electronegative value difference between carbon and hydrogen in CH3Br molecule
Electronegativity value of carbon in CH3Br = 2.55
Electronegativity value of hydrogen in CH3Br = 2.20
Difference of electronegativity value between carbon and hydrogen in CH3Br = 2.55 – 2.20 =0.35
Electronegativity difference between C-H bond calculation of CH3Brmolecule

Due to the difference in electronegativity value of less than 0.5, the C-Br bond of the CH3Br molecule becomes slight polar. Because of this difference in electronegativity, the CH3Br molecule’s C-Br bond becomes slightly polar. The electronegativity of an atom is the strength with which it may attract bound electron pairs to its side.

As a result, the C-Br bond’s dipole moment is high due to the polarization of the bonds, and C-Br bonds’ dipoles are arranged at the top of the tetrahedral molecular geometry. The CH3Br molecule’s total dipole moment is predicted to be 1.82 D. It has a partial negative charge for bromine atoms and a partial positive charge for the central carbon atom.

The electron dot structure of the CH3Br molecule is also known as the CH3Br Lewis structure. It determines the number of outermost valence electrons as well as the electrons engaged in the CH3Br molecule’s bond formation. The outermost valence electrons of the CH3Br molecule must be understood while considering the Lewis structure of the molecule.

The carbon atom is the middle element in CH3Br molecular geometry, with four electrons in its outermost valence electron shell, whereas the bromine atom has seven electrons in its outermost valence electron shell.

The CH3Br molecule has a total of 14 valence electrons as a result of the foregoing above said reasoning. With the core central carbon atom, the four terminal with one bromine and three hydrogen atoms form covalent bonds, leaving the carbon atom with no lone pairs on it.

The tetrahedral molecular geometry and structure of the CH3Br molecules are similar to that of the methane (CH4) molecule. Because no lone pair of a central carbon atom create interaction with C-Br bond pairs. The bond angle of the Br-C-H bond in the tetrahedral molecular geometry is approximately 111.5 degrees. The C-Br and C-H bond lengths are 108 and 193 pm(picometer) respectively.

To sketch the Lewis structure of CH3Br by following these instructions:

Step-1: CH3Br Lewis dot Structure by counting valence electrons on carbon atom

To calculate the valence electron of each atom in CH3Br, look for its periodic group from the periodic table. The carbon and halogen families, which are the 14th and 17th groups in the periodic table, are both made up of carbon and bromine atoms. In their outermost shells, carbon and bromine have four and seven valence electrons, respectively.

Because carbon and bromine are members of the periodic table’s carbon and halogen family groups, their valence electrons are four and seven, respectively.

Calculate the total number of valence electrons in the CH3Br molecule’s outermost valence shell. The first step is to determine how many electrons are in the CH3Br 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 CH3Br Lewis diagram. The CH3Br molecule’s core carbon atom can be represented as follows:

Total outermost valence shell electron of carbon atom in CH3Br = 4
Total outermost valence shell electron of the bromine atom in CH3Br = 7
The CH3Br molecule has one central carbon, three hydrogen, and one bromine atoms. Then the total outermost valence shell electrons can be calculated as follows
∴ Total outermost valence shell electrons available for CH3Br Lewis structure( dot structure) = 4 +1*7+ 3*1= 14 valence electrons in CH3Br
calculation of total valence electron of CH3Br molecule

Choose the atom with the least electronegative value atom and insert it in the center of the molecular geometry of CH3Br. We’ll choose the least electronegative value atom in the CH3Br molecule to place in the center of the CH3Br Lewis structure diagram in this phase. The electronegativity value in periodic groups grows from left to right in the periodic table and drops from top to bottom.

Step-2: Lewis Structure of CH3Br for constructing around the terminal hydrogen and bromine atoms

As a result, carbon is the first atom in the periodic table’s carbon family group. Bromine is the third member of the halogen family. The electronegative value of the carbon atom is lower than that of the bromine atom in the CH3Br molecule. Furthermore, carbon has a four electrons limit since bromine is the most electronegative element in the CH3Br molecule.

In the CH3Br Lewis structure diagram, the carbon atom can be the center atom of the molecule. As a result, central carbon in the CH3Br Lewis structure, with all one bromine and three hydrogens arranged in the tetrahedral geometry.

Add valence electrons around the bromine atom and add valence hydrogen atom, as given in the figure.

Step-3: Lewis dot Structure for CH3Br generated from step-1 and step-2

Connect the exterior and core central atom of the CH3Br molecule with four single bonds (one C-Br and three C-H). In this stage, use four single bonds to connect all one bromine and three hydrogen atoms on the outside of the CH3Br molecule to the central carbon atom in the middle.

Count how many electrons from the outermost valence shell have been used in the CH3Br structure so far. Each C-Br bond carries two electrons because each carbon atom is connected to one bromine and three hydrogen atoms by one C-Br and three C-H bonds. Bond pairings of C-Br and C-H are what they’re called.

So, out of the total of 14 valence electrons available for the CH3Br Lewis structure, we used 8 for the CH3Br molecule’s one C-Br and three C-H bonds. The CH3Br molecule has no lone pair electron in the center of carbon. We need to put no extra electrons in the molecular geometry of CH3Br.

Place the valence electrons in the C-H and C-Br bond pairs starting with the core carbon, three hydrogen, and one bromine atoms in the CH3Br molecule. In the CH3Br Lewis structure diagram, we always begin by introducing valence electrons from the central carbon atom(in step1). As a result, wrap around the central carbon atom’s bond pair valence electrons first (see figure for step1).

Carbon requires 8 electrons in its outermost valence shell to complete the molecular stability, 8 electrons bond pairs in C-H and C-Br bonds. Then place no electrons as a lone pair of electrons on the carbon atom of the CH3Br molecule. Carbon already shares 8 electrons to the four single C-Br and C-H bonds. Then place the valence electron in the bromine atom, it placed around seven electrons(step-2). Totally, 6 valence electrons were placed on one bromine atom of the CH3Br molecule.

We’ve positioned 8 electrons around the central carbon atom(step-3), which is represented by a dot, in the CH3Br molecular structure above. The carbon atom completes its molecular stability in the CH3Br molecule because it possesses 8 electrons in its bond pairs with one bromine and three hydrogens in the outermost valence shell.

Count how many outermost valence shell electrons have been used so far using the CH3Br Lewis structure. Four electron bond pairs are shown as dots in the CH3Br chemical structure, whereas four single bonds each contain two electrons. The outermost valence shell electrons of the CH3Br molecule are 8 +6 = 14 as a result of the calculation.

So far, we’ve used 14 of the CH3Br Lewis structure’s total 14 outermost valence shell electrons. No lone pair of electrons on the carbon atom in the tetrahedral geometry of the CH3Br molecule.

Complete the middle carbon atom stability and, if necessary, apply a covalent bond. The central carbon atom undergoes octet stability. Because it has a total of eight electrons in the outermost valence shell.

The core atom in the CH3Br Lewis structure is carbon, which is bonded to one bromine and three hydrogen atoms by four single bonds (C-Br and C-H). With the help of four single bonds, it already shares eight electrons. As a result, bromine follows the octet rule and has eight electrons surrounding it on the one terminal of the CH3Br molecule’s tetrahedral geometry.

How to calculate the formal charge on a carbon, hydrogen, and bromine atoms in CH3Br molecule?

Calculating formal charge on carbon in CH3Br:

The formal charge on the CH3Br 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 CH3Br Lewis dot structure.

To calculate the formal charge on the central carbon atom of the CH3Br molecule by using the following formula:
The formal charge on the carbon atom of CH3Br molecule= (V. E(C)– L.E(C) – 1/2(B.E))
V.E (C) = Valence electron in a carbon atom of CH3Br molecule
L.E(C) = Lone pairs of an electron in the carbon atom of the CH3Br molecule.
B.E = Bond pair electron in C atom of CH3Br molecule
calculation of formal charge on carbon atom in CH3Br molecule

The carbon core atom (four single bonds connected to one bromine and three hydrogen atoms ) of the CH3Br molecule has four valence electrons, no lone pair of electrons, and eight bonding electrons. Put these values for the carbon atom in the formula above.

Formal charge on carbon atom of CH3Br molecule = (4- 0-(8/2)) =0

In the Lewis structure of CH3Br, the formal charge on the central carbon atom is zero.

Calculating formal charge on bromine in CH3Br:

The formal charge on the CH3Br molecule’s bromine terminal atom often corresponds to the actual charge on that bromine terminal atom. In the following computation, the formal charge will be calculated on the terminal bromine atom of the CH3Br Lewis dot structure.

To calculate the formal charge on the terminal bromine atom of the CH3Br molecule by using the following formula:
The formal charge on the bromine atom of CH3Br molecule= (V. E(Br)– L.E(Br) – 1/2(B.E))
V.E (Br) = Valence electron in a bromine atom of CH3Br molecule
L.E(Br) = Lone pairs of an electron in the bromine atom of the CH3Br molecule.
B.E = Bond pair electron F atom of CH3Br molecule
calculation of formal charge on bromine atom in CH3Br molecule

The bromine core terminal (one single bond connected with the central carbon atom) of the CH3Br molecule has seven valence electrons, six lone pairs of electrons, and two bonding electrons. Put these values for the carbon atom in the formula above.

Formal charge on bromine atom of CH3Br molecule = (7- 6-(2/2)) =0

In the Lewis structure of CH3Br, the formal charge on the terminal bromine atom is zero.

Calculating formal charge on hydrogen in CH3Br:

The formal charge on the CH3Br molecule’s hydrogen terminal atom often corresponds to the actual charge on that hydrogen terminal atom. In the following computation, the formal charge will be calculated on the terminal hydrogen atom of the CH3Br Lewis dot structure.

To calculate the formal charge on the terminal hydrogen atom of the CH3Br molecule by using the following formula:
The formal charge on the terminal hydrogen atom of CH3Br molecule= (V. E(H)– L.E(H) – 1/2(B.E))
V.E (H) = Valence electron in the hydrogen atom of CH3Br molecule
L.E(H) = Lone pairs of an electron in the hydrogen atom of the CH3Brmolecule.
B.E = Bond pair electron in H atom of CH3Br molecule
calculation of formal charge on hydrogen atom in CH3Br molecule

The hydrogen terminal atom ( three hydrogen atoms ) of the CH3Br molecule has one valence electron, no lone pair of electrons, and two bonding electrons. Put these values for the carbon atom in the formula above.

Formal charge on hydrogen atom of CH3Br molecule = (1- 0-(2/2)) =0

In the Lewis structure of CH3Br, the formal charge on the terminal hydrogen atom is zero.

Summary:

In this post, we discussed the method to construct the CH3Br Lewis structure. First, the valence electrons are placed around the carbon atom. Second, place the valence electron on the bromine and hydrogen atoms. Finally, when we combined the first and second steps. It gives CH3Br Lewis structure. Need to remember that, if you follow the above-said method, you can construct molecular dot structure very easily.