Question

what is the molecular geom

Explanation:

To determine the molecular geometry of the given molecule (formaldehyde, \( \text{CH}_2\text{O} \)):

Step 1: Identify the central atom and its electron groups

The central atom is carbon (\( \text{C} \)). Let's analyze its bonding and lone pairs:

• Carbon forms a double bond with oxygen (\( \text{C}=\text{O} \)) and single bonds with two hydrogen atoms (\( \text{C}-\text{H} \), \( \text{C}-\text{H} \)).
• A double bond counts as 1 electron group, and each single bond also counts as 1 electron group. So, carbon has \( 3 \) electron groups (1 double bond + 2 single bonds) and \( 0 \) lone pairs (since carbon’s valence electrons are fully used in bonding: \( 4 \) valence electrons, with \( 2 \) in the double bond and \( 1 \) in each single bond).

Step 2: Apply VSEPR theory

VSEPR (Valence Shell Electron Pair Repulsion) theory states that electron groups around a central atom repel each other and arrange themselves to minimize repulsion. For a central atom with \( 3 \) electron groups and \( 0 \) lone pairs, the electron geometry (and molecular geometry, since there are no lone pairs) is trigonal planar.

Step 3: Confirm the geometry

In \( \text{CH}_2\text{O} \) (formaldehyde), the three electron groups (2 single bonds to H, 1 double bond to O) are arranged in a plane with bond angles of approximately \( 120^\circ \), consistent with trigonal planar geometry.

Answer:

Trigonal planar