a) Draw all the possible Lewis structures for the following ions: SeCl4 PO4 3- BrO3 b) Assign formal charges to each atom in each resonance structure (Show all your work on paper) c) indicate the most plausible Lewis structure. (Show all your work on paper) d) Indicate the approximate bond angles for each ion. a) Draw all (e) determine the names for the molecular geometry. (Show all your work on paper) (d) determine if the molecule is polar or non-polar;
The Correct Answer and Explanation is :
This is a detailed question about drawing Lewis structures, formal charges, and determining molecular geometries, polarity, and bond angles. Let’s break down the tasks:
a) Drawing Lewis Structures for SeCl₄, PO₄³⁻, and BrO₃⁻
- SeCl₄ (Selenium Tetrachloride)
- Selenium (Se) is in Group 16 and needs 8 electrons in its valence shell. Chlorine (Cl) is in Group 17 and has 7 valence electrons.
- Selenium will form single bonds with four chlorine atoms. Each chlorine atom will have three lone pairs, and selenium will have no lone pairs, forming four bonds.
- Lewis structure:
Cl | Cl—Se—Cl | Cl
- PO₄³⁻ (Phosphate Ion)
- Phosphorus (P) is in Group 15, so it can form five bonds, while oxygen (O) has six valence electrons. Since the ion has a charge of -3, it has extra electrons.
- Phosphorus will form single bonds with four oxygens, and each oxygen will carry a negative charge, except one that will have a double bond with phosphorus.
- Lewis structure:
O || O=P—O⁻ | O⁻
- BrO₃⁻ (Bromate Ion)
- Bromine (Br) is in Group 17, and oxygen (O) is in Group 16. In this ion, bromine has more than an octet.
- Bromine will form a double bond with one oxygen and single bonds with the other two, with the latter two carrying negative charges.
- Lewis structure:
O⁻ | O—Br=O | O⁻
b) Assigning Formal Charges
To assign formal charges, use the formula:
[
\text{Formal Charge} = \text{Valence electrons} – \left(\text{Lone electrons} + \frac{\text{Bonding electrons}}{2}\right)
]
- SeCl₄:
- Selenium (Se): 6 valence electrons, 0 lone electrons, 8 bonding electrons → Formal charge = 6 – (0 + 8/2) = 0
- Chlorine (Cl): 7 valence electrons, 6 lone electrons, 2 bonding electrons → Formal charge = 7 – (6 + 2/2) = 0
- PO₄³⁻:
- Phosphorus (P): 5 valence electrons, 0 lone electrons, 8 bonding electrons → Formal charge = 5 – (0 + 8/2) = 0
- Oxygen (O): 6 valence electrons, 6 lone electrons, 2 bonding electrons → Formal charge = 6 – (6 + 2/2) = -1 (on the three oxygens with single bonds)
- BrO₃⁻:
- Bromine (Br): 7 valence electrons, 2 lone electrons, 6 bonding electrons → Formal charge = 7 – (2 + 6/2) = 0
- Oxygen (O): 6 valence electrons, 6 lone electrons, 2 bonding electrons → Formal charge = 6 – (6 + 2/2) = -1 (on the two oxygens with single bonds)
c) Indicating the Most Plausible Lewis Structure
- SeCl₄: The structure with no formal charge on selenium and chlorine atoms is the most plausible.
- PO₄³⁻: The structure with a double bond between phosphorus and one oxygen, and the other oxygens carrying negative charges, is the most plausible.
- BrO₃⁻: The structure with bromine having a double bond with one oxygen and single bonds with the others carrying negative charges is the most plausible.
d) Molecular Geometry and Bond Angles
- SeCl₄: The electron pairs around selenium lead to a tetrahedral geometry with bond angles of approximately 109.5°.
- PO₄³⁻: The geometry is tetrahedral with bond angles of approximately 109.5°.
- BrO₃⁻: The geometry is trigonal pyramidal due to the lone pair on bromine, leading to bond angles of approximately 107°.
e) Polarity of the Molecule
- SeCl₄: The molecule is nonpolar because it has a symmetrical tetrahedral geometry, with chlorine atoms evenly distributed around selenium.
- PO₄³⁻: The ion is nonpolar because it has a symmetrical tetrahedral structure, and the charges are balanced.
- BrO₃⁻: The ion is polar because the trigonal pyramidal shape results in an uneven distribution of electron density, making the molecule have a dipole moment.
This overview shows the steps for drawing the structures, assigning formal charges, determining molecular geometry, and analyzing polarity. Would you like to explore any part in more detail?