Write a Lewis structure for each molecule

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Write a Lewis structure for each molecule:
a) CH2O
b) C2CL4
c) CH3NH2
d) CFCL3 (C central)

The correct answer and explanation is :

Lewis Structures for the Given Molecules:

a) CH₂O (Formaldehyde):

Formaldehyde consists of a carbon atom bonded to two hydrogen atoms and one oxygen atom. The central atom is carbon, which typically forms four bonds. Here’s how to draw the Lewis structure:

  1. Step 1: Determine the total number of valence electrons. Carbon (C) contributes 4 electrons, each hydrogen (H) contributes 1 electron, and oxygen (O) contributes 6 electrons, for a total of 4 + 2(1) + 6 = 8 electrons.
  2. Step 2: Carbon is placed in the center because it is the least electronegative atom, and oxygen and hydrogen are bonded to it. Hydrogen atoms will form single bonds with carbon.
  3. Step 3: Oxygen forms a double bond with carbon to fulfill its octet. This leaves carbon with a full octet (8 electrons) by sharing electrons with oxygen and the two hydrogen atoms.

The Lewis structure will be:

   H
   |
H—C=O

b) C₂Cl₄ (Tetrachloroethylene):

Tetrachloroethylene consists of two carbon atoms, each bonded to two chlorine atoms. The carbon atoms are connected by a double bond.

  1. Step 1: Count the valence electrons: Each carbon contributes 4, each chlorine contributes 7, for a total of 2(4) + 4(7) = 28 electrons.
  2. Step 2: The two carbon atoms are connected by a double bond to give each carbon 4 electrons. Each carbon also forms two single bonds with chlorine atoms.
  3. Step 3: Chlorine atoms are placed around the carbons and receive lone pairs to complete their octets.

The Lewis structure will be:

  Cl—C=C—Cl
   |     |
  Cl     Cl

c) CH₃NH₂ (Methylamine):

Methylamine has a central nitrogen atom bonded to three hydrogens and a methyl group (CH₃).

  1. Step 1: Count the valence electrons: Carbon contributes 4, hydrogen contributes 1 each, and nitrogen contributes 5, for a total of 4 + 3(1) + 5 = 12 electrons.
  2. Step 2: Place the nitrogen atom in the center and bond it to three hydrogens.
  3. Step 3: Carbon is bonded to nitrogen and three hydrogens.

The Lewis structure will be:

   H
   |
H—C—N—H
   |
   H

d) CFCl₃ (Chlorotrifluoromethane):

CFCl₃ consists of one carbon atom bonded to one fluorine, one chlorine, and two other chlorine atoms. The central atom is carbon.

  1. Step 1: Count the valence electrons: Carbon contributes 4, fluorine contributes 7, chlorine contributes 7 each, for a total of 4 + 7 + 3(7) = 32 electrons.
  2. Step 2: Place the carbon atom in the center. Fluorine and chlorine atoms form single bonds with carbon.
  3. Step 3: Each chlorine and fluorine atom will complete its octet with lone pairs of electrons.

The Lewis structure will be:

    F
    |
Cl—C—Cl
    |
    Cl

Explanation:

In each molecule, the goal of drawing the Lewis structure is to ensure that the atoms form stable bonds where they each follow the octet rule (with exceptions for hydrogen, which only needs 2 electrons). The structure reflects how electrons are shared in bonds and the placement of lone pairs on atoms like oxygen, chlorine, and fluorine. The most electronegative atoms, like oxygen, chlorine, and fluorine, typically attract electron density more than carbon and nitrogen, which is reflected in how the bonds and lone pairs are arranged.

  • Formaldehyde (CH₂O): Carbon shares two electrons with hydrogen atoms and two electrons with oxygen in a double bond.
  • Tetrachloroethylene (C₂Cl₄): Two carbon atoms are double-bonded to each other, and each is bonded to two chlorine atoms.
  • Methylamine (CH₃NH₂): The nitrogen atom is bonded to carbon and three hydrogens, with nitrogen being the central atom.
  • Chlorotrifluoromethane (CFCl₃): Carbon is bonded to one fluorine and three chlorine atoms, each completing their octet with lone pairs.

These structures showcase how atoms in molecules share electrons to achieve stable electron configurations.

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