Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is crucial for understanding various chemical properties and reactions. Let’s analyze each molecule:
1. SiO2 (Silicon Dioxide)
SiO2 has a linear arrangement of silicon and two oxygen atoms. Each silicon atom is bonded to two oxygen atoms in a tetrahedral arrangement, but because the molecule is a network solid, the individual bond angles are approximately 109.5 degrees. However, in terms of molecular geometry, we can describe it as having a tetrahedral shape around individual silicon atoms because it forms a continuous network.
2. BF3 (Boron Trifluoride)
In BF3, boron is bonded to three fluorine atoms. The molecular geometry is trigonal planar due to the absence of lone pairs on boron, which allows for the three fluorine atoms to arrange themselves around the boron atom at angles of approximately 120 degrees. This arrangement minimizes repulsion between the bonded electron pairs.
3. CFCl3 (Trichlorofluoromethane)
The geometry of CFCl3 is also tetrahedral. The central carbon atom is bonded to one fluorine and three chlorine atoms. Despite having different atoms around it, the carbon atom maintains a tetrahedral geometry due to the four groups of electrons, which include three chlorine atoms and one fluorine atom, ensuring an optimal arrangement with 109.5-degree bond angles.
4. H2CS (Thioformaldehyde)
H2CS has a trigonal planar structure. The central carbon atom is bonded to two hydrogen atoms and one sulfur atom. In H2CS, the presence of the double bond between carbon and sulfur influences the geometry, resulting in approximately 120-degree bond angles. Therefore, the molecule adopts a trigonal planar shape due to the arrangement of bonding pairs and the double bond between carbon and sulfur.