Molecular Geometry Shapes to Know for AP Chemistry

Understanding molecular geometry shapes is key in chemistry. These shapes influence molecular properties, reactivity, and polarity. From linear to seesaw, each geometry has unique bond angles and arrangements that help predict how molecules interact in various chemical contexts.

1. Linear

   • Bond angle: 180 degrees.
   • Occurs in molecules with two bonding pairs and no lone pairs (e.g., CO2).
   • Symmetrical shape leads to nonpolar molecules if identical atoms are present.

2. Bent

   • Bond angle: typically around 104.5 degrees.
   • Formed when there are two bonding pairs and one or more lone pairs (e.g., H2O).
   • The presence of lone pairs creates a repulsion that alters the bond angle.

3. Trigonal planar

   • Bond angle: 120 degrees.
   • Characterized by three bonding pairs and no lone pairs (e.g., BF3).
   • Flat, symmetrical shape often leads to nonpolar molecules if all substituents are the same.

4. Trigonal pyramidal

   • Bond angle: approximately 107 degrees.
   • Formed with three bonding pairs and one lone pair (e.g., NH3).
   • The lone pair pushes down on the bonding pairs, creating a pyramidal shape.

5. Tetrahedral

   • Bond angle: 109.5 degrees.
   • Consists of four bonding pairs and no lone pairs (e.g., CH4).
   • Three-dimensional shape that maximizes distance between electron pairs.

6. Trigonal bipyramidal

   • Bond angles: 90 degrees and 120 degrees.
   • Contains five bonding pairs and no lone pairs (e.g., PCl5).
   • Features two distinct types of positions: axial and equatorial.

7. Octahedral

   • Bond angle: 90 degrees.
   • Formed with six bonding pairs and no lone pairs (e.g., SF6).
   • Symmetrical shape allows for uniform distribution of electron density.

8. Square planar

   • Bond angle: 90 degrees.
   • Occurs with four bonding pairs and two lone pairs (e.g., XeF4).
   • The lone pairs are positioned opposite each other, maintaining a square shape.

9. T-shaped

   • Bond angle: approximately 90 degrees.
   • Formed with three bonding pairs and two lone pairs (e.g., ClF3).
   • The lone pairs occupy axial positions, resulting in a T-like structure.

10. Seesaw

    • Bond angles: 90 degrees and 120 degrees.
    • Occurs with four bonding pairs and one lone pair (e.g., SF4).
    • The lone pair occupies an equatorial position, creating an asymmetrical shape.