Draw a Lewis structure for each covalent molecule.

Draw a Lewis structure for each covalent molecule. a. CH3F b. N2H4

The Correct Answer and Explanation is:

Let’s draw and explain the Lewis structures for the given covalent molecules: CH₃F (methyl fluoride) and N₂H₄ (hydrazine).

a. CH₃F (Methyl Fluoride)

Step 1: Count the valence electrons.

• Carbon (C) has 4 valence electrons.
• Each hydrogen (H) atom has 1 valence electron, and there are 3 hydrogens, contributing 3 electrons.
• Fluorine (F) has 7 valence electrons.

Total valence electrons = 4 (C) + 3(1 H) + 7 (F) = 14 electrons.

Step 2: Draw the skeletal structure.
Carbon is the central atom (it can form four bonds), with three hydrogen atoms and one fluorine atom bonded to it.

Step 3: Distribute the electrons.

• Carbon will form single bonds with each of the three hydrogen atoms and the fluorine atom. This accounts for 4 bonds, each using 2 electrons.
• The remaining electrons (14 total – 8 used for bonds) will be placed as lone pairs on the fluorine atom.

Step 4: Check for octet rule.

• Carbon (C) has 4 bonds, which gives it 8 electrons (satisfied octet).
• Hydrogen atoms each have 2 electrons (satisfied duet rule).
• Fluorine has 3 lone pairs and one bond, which gives it 8 electrons (satisfied octet).

The Lewis structure of CH₃F is:

     H
     |
H—C—F
     |
     H

b. N₂H₄ (Hydrazine)

Step 1: Count the valence electrons.

• Each nitrogen (N) atom has 5 valence electrons, and there are 2 nitrogen atoms, contributing 10 electrons.
• Each hydrogen (H) atom has 1 valence electron, and there are 4 hydrogens, contributing 4 electrons.

Total valence electrons = 10 (N) + 4 (H) = 14 electrons.

Step 2: Draw the skeletal structure.

• The two nitrogen atoms will be connected by a single bond.
• Each nitrogen atom will form single bonds with two hydrogen atoms.

Step 3: Distribute the electrons.

• The nitrogen-nitrogen single bond uses 2 electrons.
• Each nitrogen-hydrogen bond uses 2 electrons, accounting for 8 electrons in total for the bonds.
• The remaining 4 electrons will be placed as lone pairs on the nitrogen atoms.

Step 4: Check for octet rule.

• Each nitrogen atom will have 2 single bonds with hydrogen and a single bond to the other nitrogen. Each nitrogen has 8 electrons in total (6 from bonds and 2 from lone pairs), satisfying the octet rule.
• Each hydrogen atom has 2 electrons, fulfilling the duet rule.

The Lewis structure of N₂H₄ is:

H—N—N—H
     |
     H
     |
     H

Conclusion:

• In CH₃F, carbon bonds to three hydrogens and one fluorine atom, with fluorine having lone pairs to complete its octet.
• In N₂H₄, each nitrogen bonds to two hydrogens and the other nitrogen, with lone pairs completing the nitrogen octets.

Both molecules satisfy the octet (or duet for hydrogen) rule, making the structures stable.