What is the molecular shape of a silicon dioxide molecule, SiO2? Select one: a. tetrahedral b. linear c. trigonal pyramidal d. trigonal planar e. bent
The correct answer and explanation is :
The correct answer is b. linear.
Explanation:
Silicon dioxide (SiO₂) is a molecule consisting of silicon (Si) atoms covalently bonded to oxygen (O) atoms. The molecular shape of SiO₂ is determined by the arrangement of atoms in the molecule and the bonding between them.
SiO₂ is often found in a network structure, such as in quartz, where each silicon atom is bonded to four oxygen atoms in a tetrahedral arrangement. However, when we refer to a “SiO₂ molecule,” particularly in terms of molecular geometry, we consider the simplest representation of the molecule, which is a dimeric unit consisting of two silicon atoms bonded to two oxygen atoms.
Key Points in the Structure of SiO₂:
- Bonding: In the simplest molecular form, SiO₂ can be thought of as having a linear structure. Each silicon atom is bonded to two oxygen atoms, with the oxygen atoms also being bonded to one another. The Si-O-Si bond angle in this arrangement is 180°, giving the molecule a linear geometry.
- Electron Domains and Geometry: Each silicon atom in SiO₂ typically forms two sigma bonds with oxygen atoms and has no lone pairs, making the geometry around each silicon atom linear according to VSEPR (Valence Shell Electron Pair Repulsion) theory. Oxygen atoms in SiO₂, on the other hand, form bonds but do not have lone pairs contributing to the molecular geometry.
- Network vs Molecular Form: While SiO₂ is commonly seen in a network (like in quartz), which has a three-dimensional tetrahedral structure, when considering the molecular form of SiO₂, it adopts a linear shape as a molecule.
In summary, when you consider the molecule SiO₂, the simplest molecular shape is linear, and this choice corresponds to the correct answer.