Each year around 2 x 106 tons of chloromethane reaches the stratosphere which is almost 25% of the total chlorine emitted annually. Chloromethane is harmful to the environment as it mixes with various natural sinks to reach all the land, air, and water ecosystems. Chloromethane is a stable molecule but being in high concentration and the ever-changing climatic pattern has what made it a deadly one to deal with altogether.
Lewis Structure of Chloromethane (CH3Cl)
The Lewis structure is a pictorial representation showing the electrons present in the valence shell in an atom. The diagram is drawn to determine how the valence electrons of different atoms participate in the bond formation to form a molecule. Within the diagram, the ‘dots’ nearby the symbol of an element represents the valence electrons. If you realize, these valence electrons are always written in pair at each side of the symbol to show if all paired electrons exist or not. In addition to this, the Lewis structure also determines whether a single, double or triple bond is formed between the interacting atoms.
How to draw Lewis Structure of CH3Cl?
To begin with the Lewis structure of CH3Cl, first, we need to determine the electronic configuration of each participating atom. The atomic number of Hydrogen (H) is 1, so its electronic configuration is 1s1. As the s shell needs two electrons, there is a vacancy of one electron, so the number of valence electrons in one Hydrogen (H) atom is 1. In the case of Carbon (C), its atomic number is 6, so the electronic configuration is 1s2 2s2 2p2. This makes the number of valence electrons in one Carbon (C) 4. Lastly for Chlorine (Cl), the atomic number is 17 where its electronic configuration is 1s2 2s2 2p6 3s2 3p5. So, the number of valence electrons in the outermost shell for Chlorine (Cl) is 7. Now, let us study the step-by-step method for drawing the Lewis structure of Chloromethane (CH3Cl). Step 1: Find the central atom: Usually, single-atom with the least electronegativity becomes the central atom. In the case of CH3Cl, there are only two single atoms C and Cl, where their electronegativity values are 2.6 and 3.2. As the Carbon (C) atom has a lower value, so it will be the central atom. Step 2: Figure out the total number of participating valence electrons: This will be figured by adding up the valence electrons of all the atoms. In the case of CH3Cl, the total number of valence electrons will be 14. Step 3: Figure out how many more electrons are required to stabilize one CH3Cl molecule: One CH3Cl molecule needs 8 more electrons to stabilize its structure completely. Step 4: Look for the number and type of bond-forming in a CH3Cl molecule: In the case of Ch3Cl, only single covalent bonds are forming between the participating atoms. Step 5: Now draw the Lewis diagram assembling the aforementioned steps.
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Molecular Geometry of CH3Cl
The CH3Cl is a Penta atomic molecule with a bond angle of 109.5° which gives the molecule a bent shape. The molecular geometry of a molecule can be studied with the help of the Valence Shell Electron Pair Repulsion (VSEPR) theory which says chloromethane (CH3Cl) has a tetrahedral shape as the bond angle is 109.5° with the Carbon (C), always as the central atom. Moreover, no distortion in the structure occurs as there is no lone pair in the CH3Cl molecule because of which each bond is of equal angle and present at equal distance from one another as all the single bonds are contributing to equal repulsion. Below is the 3D representation of the CH3Cl molecule. Have a look!
Is Chloromethane (CH3Cl) Polar or Non-Polar?
Polar molecules are those where the electronegativity difference between the two participating atoms is huge which leads to the separation of charges. Due to this, one end withholds a positive charge whereas the other one acquires a negative charge. On the other hand, non-polar molecules are those where the electronegativity difference between the participating molecules is not much and almost negligible. This does not lead to separation of charges and the molecule remains in a stable state with no intention to bond with other nearby atoms, under normal conditions. To figure out the answer to this question, it is important to determine and compare the electronegativity values of all the participating atoms. In the case of Carbon (C) and Chlorine (Cl) atoms, Cl (3.2) is more electronegative than C (2.6) so the dipole behavior moves from downward to upward direction. Moreover, the electronegativity values of Hydrogen (2.20) and Carbon are so close that their difference is negligible which makes the H-C bond non-polar. But, as the C-Cl bond is polar, the whole CH3Cl molecule carries a net dipole moment making the molecule polar. The electronegativity moving in the upward direction between the C-Cl bond is what makes the CH3Cl molecule polar. you should also once read out the dedicated article written on the polarity of CH3Cl.
CH3Cl Hybridization
Hybridization is a concept that says atomic orbitals of different chemical elements, mix and intermix with one another to produce new hybrid molecules that influences both the molecular geometry and the chemical bonding nature of the molecule. A detail about this can be studied with the help of the Valence Bond Theory to understand how the central atom within a molecule undergoes hybridization like sp, sp2, sp3, and others. The hybridization of the central atom i.e., Carbon in CH3Cl molecule is sp3. It is because the CH3Cl molecule has four single bonds and no lone pair of electrons. When we talk about finding the hybridization of a molecule, we always take the shells which are far away from the nucleus. In the case of Carbon, these shells are 2s2 and 2p2 where the paired electrons will first fill the 2s shell then 2px and 2py. But this situation is not possible as the four single bonds need to be accommodated in all the 2s, 2px, 2py, and 2pz shells. To accomplish this, each electron hybridizes and fills all the 2s, 2px, 2py, and 2pz shells providing the chance to four single bonds to fill the space. This makes the central carbon atom sp3 hybridized where the three hydrogen atoms are s-sp3 hybridized and the single chlorine atom is sp3-p hybridized.
Molecular Orbital Diagram of CH3Cl
The molecular orbital diagram is a pictorial representation of how chemical bonding is taking place within a molecule, in alignment with the rules of molecular orbital theory and the linear combination of atomic orbitals. The idea behind drawing the molecular orbital diagram is, some of the atomic orbitals combine to form new molecular orbitals, but in the same number. Here, the participating electrons tend to redistribute themselves into different orbitals to produce hybridized orbitals. The main aim of the molecular orbital diagrams is to determine the energy levels of the participating orbitals and compare them to figure out how bonding took place in a molecule.
In the case of a single bond, only sigma bond (σ) is present with no pi (π) bond. The above-mentioned diagrams show how hybridization takes place within a molecule providing a reason why one molecule decided to bind with the other one, only. The Carbon and Hydrogen atoms having almost similar electronegativity values tend to behave in a similar fashion, even when it comes to the energy levels of their respective orbitals. Whereas, the Carbon and Chlorine having a greater difference between their electronegativity values tend to make different sizes of lobes showing a prominent difference in their energy levels.
Conclusion
Chloromethane (CH3Cl) is a stable compound where the atoms are in a stable condition and do not easily react with other elements under normal conditions. The Lewis structure can easily help with predicting the molecular geometry, hybridization, polarity, and a molecular orbital diagram for the CH3Cl molecule. It is because the CH3Cl molecule is highly stable with no distortion in the structure, the molecule is one of the easiest Penta-atomic structures to study and learn about how to predict different energy levels of the orbitals with the help of a molecular orbital diagram.
