Draw the Lewis structure of formaldehyde (H
CO) and then determine if the molecule is polar or nonpolar. + A) Nonpolar B) Polar
The Correct Answer and Explanation is:
To determine the polarity of formaldehyde (H₂CO), start by drawing its Lewis structure. Formaldehyde consists of one carbon atom, one oxygen atom, and two hydrogen atoms. Follow these steps:
- Count the total number of valence electrons:
- Carbon has four valence electrons.
- Oxygen has six valence electrons.
- Each hydrogen has one valence electron.
- The total number of valence electrons is 12.
- Identify the central atom:
- Carbon is the central atom because it forms multiple bonds and has the lowest electronegativity among the non-hydrogen atoms.
- Arrange the atoms:
- Place the carbon atom in the center.
- Bond the oxygen to the carbon.
- Attach the two hydrogen atoms to carbon.
- Distribute electrons:
- Create a double bond between carbon and oxygen to satisfy their octets.
- Carbon forms two single bonds with hydrogen atoms.
- Oxygen has two lone pairs.
The Lewis structure is as follows:
H | H – C = O
Now evaluate the polarity. The carbon-oxygen bond is polar due to oxygen’s higher electronegativity, which pulls electron density toward itself. Additionally, formaldehyde adopts a trigonal planar geometry, meaning the dipoles do not cancel out. As a result, the molecule has a net dipole moment, making it polar. Therefore, the correct answer is B) Polar. The molecular shape and electronegativity difference ensure the molecule has an uneven charge distribution, resulting in its polarity. This affects properties like solubility and intermolecular interactions.
