Predict the molecular structure and bond angles for each molecule or ion given below: PO43-: tetrahedral XeO4: tetrahedral POCl3: trigonal pyramid CIO4: tetrahedral CIO3-: tetrahedral SO3: trigonal pyramid NF3: V-shaped SO42-: tetrahedral molecular structure bond angles
The Correct Answer and Explanation is:
Let’s break down each molecule or ion:
- PO4^3- (Phosphate ion):
- Molecular structure: Tetrahedral.
- Bond angles: Approximately 109.5°.
- Explanation: In PO4^3-, the central phosphorus atom is bonded to four oxygen atoms, with each oxygen carrying a negative charge. This leads to a tetrahedral structure due to electron pair repulsion, where the bond angles are close to 109.5°.
- XeO4 (Xenon tetroxide):
- Molecular structure: Tetrahedral.
- Bond angles: Approximately 109.5°.
- Explanation: Xenon is in the center, bonded to four oxygen atoms. The xenon atom in XeO4 has no lone pairs, so the molecule adopts a tetrahedral geometry, similar to methane, with bond angles of around 109.5°.
- POCl3 (Phosphorus trichloride oxide):
- Molecular structure: Trigonal pyramid.
- Bond angles: Approximately 107°.
- Explanation: The phosphorus atom is surrounded by three chlorine atoms and one lone pair. This leads to a trigonal pyramidal structure, with bond angles slightly less than 109.5°, approximately 107° due to the lone pair.
- ClO4- (Perchlorate ion):
- Molecular structure: Tetrahedral.
- Bond angles: Approximately 109.5°.
- Explanation: The central chlorine atom is bonded to four oxygen atoms in a tetrahedral arrangement. Since there are no lone pairs on the chlorine atom, the bond angles remain around 109.5°.
- ClO3- (Chlorate ion):
- Molecular structure: Tetrahedral.
- Bond angles: Approximately 109.5°.
- Explanation: Similar to the perchlorate ion, chlorine is surrounded by three oxygen atoms and a lone pair. Although there’s a lone pair, the overall structure still tends to follow tetrahedral geometry, leading to bond angles near 109.5°, but slightly distorted.
- SO3 (Sulfur trioxide):
- Molecular structure: Trigonal planar (Not trigonal pyramidal).
- Bond angles: 120°.
- Explanation: The sulfur atom is bonded to three oxygen atoms in a trigonal planar arrangement, and the bond angles are 120° due to no lone pairs on the sulfur atom.
- NF3 (Nitrogen trifluoride):
- Molecular structure: V-shaped (Bent).
- Bond angles: Approximately 102°.
- Explanation: In NF3, nitrogen is bonded to three fluorine atoms, but due to a lone pair on nitrogen, the molecule adopts a V-shaped structure. The bond angles are slightly less than 109.5°, around 102°.
- SO4^2- (Sulfate ion):
- Molecular structure: Tetrahedral.
- Bond angles: 109.5°.
- Explanation: The sulfur atom is surrounded by four oxygen atoms in a tetrahedral geometry, and there are no lone pairs on the sulfur atom. The bond angles are about 109.5°.
In summary:
- Tetrahedral structures: PO4^3-, XeO4, ClO4-, ClO3-, SO42-.
- Trigonal pyramidal structures: POCl3.
- Trigonal planar: SO3.
- V-shaped (Bent): NF3.
Most of these molecules and ions follow the VSEPR model, where electron pair repulsion determines the molecular geometry and bond angles.
