How to Draw Lewis Structures for Acetaldehyde (CH3CHO), Chloroethene (C2H3F), and Chloroethyne (C2HCl)?

To draw the Lewis structures for these molecules, we need to follow a systematic approach that includes determining the total number of valence electrons available and then arranging the atoms to satisfy the octet rule where applicable.

1. Acetaldehyde (CH₃CHO)

Acetaldehyde consists of two carbon atoms, one oxygen atom, and four hydrogen atoms. The total number of valence electrons is:

• Carbon (C): 4 electrons × 2 = 8
• Oxygen (O): 6 electrons × 1 = 6
• Hydrogen (H): 1 electron × 4 = 4

Total = 8 + 6 + 4 = 18 valence electrons.

The structure can be built as follows:

1. Arrange the carbon atoms in the center, with one carbon atom connected to three hydrogens (CH₃) and the other connected to one hydrogen and an oxygen (CHO).
2. Connect the two carbon atoms with a single bond.
3. Connect the oxygen atom to the second carbon with a double bond and the remaining hydrogen to the oxygen with a single bond.

The final Lewis structure looks like this:

2. Chloroethene (C₂H₃F)

This molecule has two carbon atoms, three hydrogen atoms, and one fluorine atom. The total number of valence electrons is:

• Carbon (C): 4 electrons × 2 = 8
• Hydrogen (H): 1 electron × 3 = 3
• Fluorine (F): 7 electrons × 1 = 7

Total = 8 + 3 + 7 = 18 valence electrons.

For chloroethene:

1. Begin with the two carbon atoms, connect them with a double bond.
2. Attach the three hydrogen atoms to one carbon and the fluorine atom to the other carbon.

The Lewis structure is shown below:

3. Chloroethyne (C₂HCl)

Chloroethyne consists of two carbon atoms, one hydrogen atom, and one chlorine atom. The total number of valence electrons is:

• Carbon (C): 4 electrons × 2 = 8
• Hydrogen (H): 1 electron × 1 = 1
• Chlorine (Cl): 7 electrons × 1 = 7

Total = 8 + 1 + 7 = 16 valence electrons.

For chloroethyne:

1. Connect the two carbon atoms with a triple bond.
2. Attach the hydrogen atom to one of the carbon atoms and the chlorine atom to the other.

The resulting Lewis structure is as follows:

In summary, drawing Lewis structures involves knowing the total number of valence electrons and properly arranging atoms to reflect bonds and formal charges, ensuring each atom has a full outer shell where possible.