Draw the Lewis Dot Structure for Acetamide (CH3CONH2) and Determine the Formal Charge of Each Atom of This Molecule

To draw the Lewis dot structure for acetamide (CH₃CONH₂), we start by calculating the total number of valence electrons available in the molecule. Acetamide consists of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) atoms. The counts are as follows:

• C has 4 valence electrons. There are 2 carbon atoms in the molecule.
• There are 2 nitrogen atoms, each contributing 5 valence electrons.
• There are 3 hydrogen atoms, each contributing 1 valence electron.
• Oxygen contributes 6 valence electrons.

Therefore, the total number of valence electrons is:

Total = (2 x 4) + (6) + (2 x 1) + (5) = 4 + 6 + 2 + 5 = 17 valence electrons.

Next, we can start drawing the Lewis structure. The structure generally starts with the carbon atom in the center. The structure looks like this:

In the Lewis structure:

• The carbon atom is bonded to three hydrogen atoms (each using 1 valence electron).
• The carbon is also bonded to the oxygen atom by a double bond (using 4 valence electrons). The oxygen has two lone pairs of electrons.
• The carbon is further bonded to the nitrogen atom with a single bond (using 2 valence electrons). The nitrogen also has two lone pairs of electrons.

Now, let’s determine the formal charge for each atom in the molecule using the formula:

Formal Charge = Valence Electrons – (Nonbonding Electrons + 0.5 * Bonding Electrons)

• For carbon (C):
• Valence Electrons = 4
• Nonbonding Electrons = 0
• Bonding Electrons = 8 (3 single bonds and 1 double bond)
• Formal Charge = 4 – (0 + 0.5 * 8) = 4 – 4 = 0
• For oxygen (O):
• Valence Electrons = 6
• Nonbonding Electrons = 4 (two lone pairs)
• Bonding Electrons = 4 (2 from the double bond)
• Formal Charge = 6 – (4 + 0.5 * 4) = 6 – 6 = 0
• For nitrogen (N):
• Valence Electrons = 5
• Nonbonding Electrons = 4 (two lone pairs)
• Bonding Electrons = 2 (1 single bond with carbon)
• Formal Charge = 5 – (4 + 0.5 * 2) = 5 – 5 = 0
• For each hydrogen (H):
• Valence Electrons = 1
• Nonbonding Electrons = 0
• Bonding Electrons = 2 (single bonds with carbon or nitrogen)
• Formal Charge = 1 – (0 + 0.5 * 2) = 1 – 1 = 0

In conclusion, each atom in the acetamide molecule has a formal charge of 0, indicating that the Lewis structure is stable. This structure reflects the arrangement of electrons in the molecule, ensuring that all atoms follow the octet rule where applicable.