Draw the best Lewis Dot Structure for each of the following species. Give the molecular geometry and shapes of these molecules using VSEPR. a) BeF2 b) BCl3 c) CCl4 d) PBr5 e) SiCl6 f) BH3 g) NI3 h) ClF i) SF6
The Correct Answer and Explanation is:
Here’s the best Lewis Dot Structure for each species, along with the molecular geometry and shapes based on VSEPR theory:
a) BeF2 (Beryllium Fluoride)
- Lewis Structure: Beryllium (Be) is the central atom with two fluorine (F) atoms attached. Be has two valence electrons, and each F has seven. In the Lewis structure, Be forms single bonds with both F atoms, and each F gets three lone pairs of electrons.
- Molecular Geometry: Linear.
- Shape: The molecule is linear, with a bond angle of 180°.
b) BCl3 (Boron Trichloride)
- Lewis Structure: Boron (B) is the central atom, surrounded by three chlorine (Cl) atoms. Boron has three valence electrons, and each Cl has seven. The Lewis structure shows three single bonds between B and Cl, with each Cl having three lone pairs.
- Molecular Geometry: Trigonal planar.
- Shape: The molecule is trigonal planar with 120° bond angles.
c) CCl4 (Carbon Tetrachloride)
- Lewis Structure: Carbon (C) is the central atom, surrounded by four chlorine (Cl) atoms. Carbon has four valence electrons, and each chlorine has seven. The structure shows four single bonds between C and Cl, with each Cl having three lone pairs.
- Molecular Geometry: Tetrahedral.
- Shape: The molecule has a tetrahedral shape, with 109.5° bond angles.
d) PBr5 (Phosphorus Pentabromide)
- Lewis Structure: Phosphorus (P) is the central atom, with five bromine (Br) atoms surrounding it. Phosphorus has five valence electrons, and each bromine has seven. The structure shows five single bonds between P and Br, with each Br having three lone pairs.
- Molecular Geometry: Trigonal bipyramidal.
- Shape: The molecule adopts a trigonal bipyramidal shape with bond angles of 90° and 120°.
e) SiCl6 (Silicon Hexachloride)
- Lewis Structure: Silicon (Si) is the central atom, surrounded by six chlorine (Cl) atoms. Silicon has four valence electrons, and each chlorine has seven. The structure shows six single bonds between Si and Cl, with each Cl having three lone pairs.
- Molecular Geometry: Octahedral.
- Shape: The molecule adopts an octahedral shape, with 90° bond angles.
f) BH3 (Borane)
- Lewis Structure: Boron (B) is the central atom, with three hydrogen (H) atoms attached. Boron has three valence electrons, and each hydrogen has one. The structure shows three single bonds between B and H, with no lone pairs on B.
- Molecular Geometry: Trigonal planar.
- Shape: The molecule is trigonal planar, with 120° bond angles.
g) NI3 (Nitrogen Triiodide)
- Lewis Structure: Nitrogen (N) is the central atom, surrounded by three iodine (I) atoms. Nitrogen has five valence electrons, and each iodine has seven. The structure shows three single bonds between N and I, with each iodine having three lone pairs.
- Molecular Geometry: Trigonal pyramidal.
- Shape: The molecule is trigonal pyramidal, with bond angles slightly less than 109.5° due to the lone pair on nitrogen.
h) ClF (Chlorine Monofluoride)
- Lewis Structure: Chlorine (Cl) is the central atom, with one fluorine (F) atom attached. Chlorine has seven valence electrons, and fluorine has seven. The structure shows a single bond between Cl and F, with three lone pairs on Cl and three lone pairs on F.
- Molecular Geometry: Linear.
- Shape: The molecule is linear, with a bond angle of 180°.
i) SF6 (Sulfur Hexafluoride)
- Lewis Structure: Sulfur (S) is the central atom, surrounded by six fluorine (F) atoms. Sulfur has six valence electrons, and each fluorine has seven. The structure shows six single bonds between S and F, with each F having three lone pairs.
- Molecular Geometry: Octahedral.
- Shape: The molecule adopts an octahedral shape, with 90° bond angles.
In summary, these molecules can be understood by looking at their Lewis structures and considering their bonding and lone pairs. The VSEPR theory then provides a way to predict their geometry based on minimizing repulsions between electron pairs.
