Draw the Lewis structure for H2O, CH4 (methane), and for NH3

1. Draw the Lewis structure for H2O, CH4 (methane), and for NH3.
2. Write the Lewis structure of the following molecules:

a. Ethylene, C2H4

b. Acetylene, C2H2

c. Carbon tetrachloride, CCl4

d. COBr2 (for the skeletal structure, C is bonded to O and Br atoms)

The Correct Answer and Explanation is :

Here are the Lewis structures for the given molecules, followed by a detailed explanation:

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1. Lewis Structures

a. Water (H₂O):

• Central atom: Oxygen.
• Each hydrogen atom forms a single bond with oxygen.
• Oxygen has two lone pairs of electrons.

   H
   |
H—O
   |
   H

b. Methane (CH₄):

• Central atom: Carbon.
• Carbon forms single bonds with four hydrogen atoms.
• Carbon has no lone pairs.

    H
    |
H—C—H
    |
    H

c. Ammonia (NH₃):

• Central atom: Nitrogen.
• Nitrogen forms three single bonds with hydrogen atoms.
• Nitrogen has one lone pair of electrons.

    H
    |
H—N—H
    ..

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2. Lewis Structures

a. Ethylene (C₂H₄):

• Each carbon atom forms a double bond with the other carbon and single bonds with two hydrogen atoms.

H   H
 \ /
  C=C
 / \
H   H

b. Acetylene (C₂H₂):

• Carbon atoms are triple-bonded to each other, with each carbon forming a single bond to one hydrogen atom.

H-C≡C-H

c. Carbon tetrachloride (CCl₄):

• Carbon forms single bonds with four chlorine atoms, each chlorine atom has three lone pairs.

   Cl
   |
Cl-C-Cl
   |
   Cl

d. COBr₂:

• Carbon is bonded to oxygen (double bond) and two bromine atoms (single bonds). Oxygen has two lone pairs, and bromine atoms each have three lone pairs.

   Br
   |
O=C
   |
   Br

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Explanation (Approx. 300 Words)

The Lewis structure illustrates the arrangement of atoms, bonds, and lone pairs in a molecule. Electrons are shown as dots, while bonds are depicted as lines. Here’s a breakdown of the reasoning:

1. Octet Rule: Atoms aim to complete their octet (8 valence electrons), except hydrogen, which requires only 2 electrons.
2. Steps to Draw a Lewis Structure:

• Count total valence electrons for all atoms.
• Arrange atoms with the least electronegative atom (except hydrogen) in the center.
• Form single bonds, then add double/triple bonds as needed.
• Distribute lone pairs to satisfy the octet rule.

1. Key Insights:

• Water (H₂O): Oxygen has 6 valence electrons, shares 2 electrons with hydrogens, and retains 2 lone pairs.
• Methane (CH₄): Carbon shares its 4 valence electrons equally with hydrogen atoms.
• Ammonia (NH₃): Nitrogen shares 3 electrons with hydrogens, leaving 1 lone pair.
• Ethylene (C₂H₄): A double bond between carbons satisfies their octets while hydrogens form single bonds.
• Acetylene (C₂H₂): A triple bond between carbons ensures octet fulfillment; each carbon also bonds to one hydrogen.
• Carbon tetrachloride (CCl₄): Carbon forms single bonds with four chlorine atoms, completing all octets.
• COBr₂: The skeletal structure places oxygen (double bond) and bromine (single bonds) around carbon, adhering to the octet rule.