Draw the Lewis structure of H2CO

Draw the Lewis structure of H₂CO, then answer the following questions.

The electron group geometry of H₂CO is –linear bent or angular/ trigonal planar/ tetrahedral/ trigonal pyramid.

The molecular shape of H₂CO is —linear bent or angular/ trigonal planar/ tetrahedral/ trigonal pyramid.

The C-O bond is –polar/ non polar.

The H-C-H bond angle is approximately –90° /109°/ 120°/180°.

A H₂CO molecule is –polar/ nonpolar.

The correct answer and explanation is :

Lewis Structure of H₂CO (Formaldehyde)

Formaldehyde (H₂CO) consists of one carbon (C), one oxygen (O), and two hydrogen (H) atoms. The Lewis structure of H₂CO is drawn as follows:

1. Determine the total number of valence electrons:

• Carbon (C) has 4 valence electrons.
• Oxygen (O) has 6 valence electrons.
• Hydrogen (H) has 1 valence electron (×2 = 2 total).
• Total: 4 + 6 + 2 = 12 valence electrons.

1. Arrange the atoms:

• Carbon is the central atom since it is the least electronegative (excluding hydrogen).
• Oxygen and hydrogen are attached to carbon.

1. Distribute electrons:

• Carbon forms two single bonds with hydrogen.
• Carbon forms a double bond with oxygen.
• The oxygen has two lone pairs.

Thus, the Lewis structure is:

      O
     ║
H — C — H

Oxygen has a double bond with carbon, and each hydrogen forms a single bond with carbon.

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Answers to the Questions:

1. Electron Group Geometry: Trigonal Planar

• The electron geometry is determined by the number of electron domains (bonding and lone pairs) around the central atom. Carbon has three regions of electron density (two single bonds to hydrogen and one double bond to oxygen), which leads to a trigonal planar electron geometry.

1. Molecular Shape: Trigonal Planar

• Since there are no lone pairs on carbon, the molecular shape remains trigonal planar.

1. C-O Bond Polarity: Polar

• The carbon-oxygen bond is polar because oxygen is significantly more electronegative than carbon, causing a partial negative charge on oxygen and a partial positive charge on carbon.

1. H-C-H Bond Angle: 120°

• In a trigonal planar structure, the ideal bond angle is 120°.

1. Polarity of the H₂CO Molecule: Polar

• The molecule is polar because the C=O bond creates a dipole moment, which does not cancel out due to the asymmetrical distribution of charge.

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Explanation (300 Words)

The structure of formaldehyde (H₂CO) consists of a central carbon atom bonded to two hydrogen atoms and one oxygen atom via a double bond. To determine its electron geometry, we count the electron domains around carbon, which include three regions (one double bond and two single bonds). Since three regions of electron density adopt a trigonal planar arrangement to minimize repulsion, the electron geometry of H₂CO is trigonal planar.

The molecular shape is also trigonal planar, since there are no lone pairs on the central carbon to distort the geometry. The C-O bond is polar due to the electronegativity difference between carbon (~2.5) and oxygen (~3.5), making oxygen partially negative and carbon partially positive. This dipole does not cancel out because the molecular shape is asymmetric.

Since the molecule follows a trigonal planar geometry, the H-C-H bond angle is approximately 120°, consistent with the expected angles in a planar structure.

Regarding molecular polarity, although the H-C bonds are relatively nonpolar, the strong C=O bond dipole dominates the molecule’s polarity, making H₂CO a polar molecule. This polarity allows H₂CO to dissolve in polar solvents like water and participate in hydrogen bonding interactions via its oxygen atom.

Overall, the shape, bond polarity, and molecular polarity of H₂CO significantly influence its physical and chemical properties, including its ability to act as a reactive electrophile in organic synthesis and biological systems.