Write the Lewis structure for each molecule.

Write the Lewis structure for each molecule. a. CH2O b. C2Cl4

The Correct Answer and Explanation is:

a. CH₂O (Formaldehyde)

Lewis Structure:

mathematicaCopyEdit   H
   |
H–C=O
     ||
     O

Explanation:

Formaldehyde (CH₂O) consists of one carbon (C), two hydrogen (H), and one oxygen (O) atom. Here’s how we draw its Lewis structure:

1. Count total valence electrons:
   • Carbon (Group 14): 4 electrons
   • Hydrogen (Group 1): 1 electron × 2 = 2 electrons
   • Oxygen (Group 16): 6 electrons
   • Total = 4 + 2 + 6 = 12 valence electrons
2. Determine the central atom:
   Carbon is the central atom because it can form 4 bonds, while H and O typically form 1 and 2 bonds respectively.
3. Create single bonds between C and H, and C and O:
   • Each bond uses 2 electrons: 3 single bonds = 6 electrons used.
4. Distribute remaining electrons:
   • 6 electrons remain. Place them as lone pairs on oxygen.
5. Check octet rule:
   • Carbon has only 6 electrons; to complete its octet, form a double bond with oxygen.
   • Final bonding: 2 single bonds (C–H), 1 double bond (C=O).
6. Final structure: Carbon forms two single bonds with H and a double bond with O. Oxygen has two lone pairs, satisfying the octet rule.

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b. C₂Cl₄ (Tetrachloroethylene)

Lewis Structure:

mathematicaCopyEdit   Cl     Cl
    \     /
     C = C
    /     \
  Cl       Cl

Explanation:

Tetrachloroethylene has two carbon (C) atoms and four chlorine (Cl) atoms.

1. Count total valence electrons:
   • Carbon: 4 × 2 = 8 electrons
   • Chlorine: 7 × 4 = 28 electrons
   • Total = 36 valence electrons
2. Determine structure:
   • Carbon atoms form a double bond (C=C) in the center.
   • Each carbon is also bonded to two chlorine atoms (4 single bonds total).
3. Assign lone pairs:
   • Chlorine atoms get 3 lone pairs each (6 electrons × 4 = 24 electrons).
   • The double bond and single bonds account for 12 electrons (6 bonds × 2 electrons).
4. Octet rule:
   • Each atom satisfies the octet. Carbon atoms have 4 bonds each (8 electrons), chlorine has 1 bond and 3 lone pairs (also 8 electrons).
5. Final structure: Two central carbon atoms form a double bond, each bonded to two chlorine atoms.

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These Lewis structures illustrate correct electron pairing and bonding based on valence electron rules and the octet principle.