6) A) Draw the Lewis structure of HBrO
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where the structure obeys octet rule. What is the electronic geometry? B) Draw the structure where the formal charges are minimized. Draw in the bond dipoles. What is the electronic geometry? C) Determine the Steric number and molecular geometry around the central atom in part B. Determine the molecular
The correct answer and explanation
iturn0image0turn0image1turn0image2Bromic acid (HBrO₃) consists of a hydrogen atom (H), a bromine atom (Br), and three oxygen atoms (O). To understand its structure and properties, we can analyze its Lewis structures, electronic geometry, and molecular geometry.
A) Lewis Structure of HBrO₃ Obeying the Octet Rule and Its Electronic Geometry
To draw the Lewis structure of HBrO₃ while ensuring that each atom satisfies the octet rule:
- Count the total valence electrons: Hydrogen has 1 valence electron, bromine has 7, and each oxygen has 6. Thus, the total is:
- 1 (H) + 7 (Br) + 3×6 (O) = 26 valence electrons.
- Determine the central atom: Bromine is less electronegative than oxygen and can form multiple bonds, making it the central atom. Hydrogen, being able to form only one bond, is always a terminal atom.
- Connect atoms with single bonds initially: Place bromine at the center, bond it to three oxygen atoms, and bond one of these oxygens to hydrogen. This accounts for 4 bonds (8 electrons).
- Distribute remaining electrons to satisfy the octet rule:
- Each of the two oxygens not bonded to hydrogen receives 6 electrons (3 lone pairs), totaling 12 electrons.
- The oxygen bonded to hydrogen has 4 additional electrons (2 lone pairs), totaling 6 electrons.
- This uses up all 26 valence electrons.
- Check formal charges: In this arrangement, bromine has a formal charge of +2, and the two doubly-bonded oxygens have formal charges of -1 each, leading to an unstable structure.
- Adjust for stability: To minimize formal charges, convert two lone pairs from the negatively charged oxygens into double bonds with bromine. This results in:
- Bromine forming two double bonds with two oxygens and a single bond with the hydroxyl group (OH).
- All atoms now have formal charges of zero, indicating a more stable structure.
Electronic Geometry: With three regions of electron density around the central bromine atom (two double bonds and one single bond with the OH group), the electronic geometry is trigonal planar.
B) Lewis Structure with Minimized Formal Charges, Bond Dipoles, and Electronic Geometry
As derived above, the Lewis structure with minimized formal charges has bromine double-bonded to two oxygens and single-bonded to an OH group.
Bond Dipoles:
- Br=O Bonds: Oxygen is more electronegative than bromine, so the dipole arrows point from bromine to oxygen.
- Br-OH Bond: Oxygen is more electronegative than bromine, so the dipole arrow points from bromine to oxygen.
- O-H Bond: Oxygen is more electronegative than hydrogen, so the dipole arrow points from hydrogen to oxygen.
Electronic Geometry: The electronic geometry remains trigonal planar, as there are still three regions of electron density around bromine.
C) Steric Number and Molecular Geometry Around the Central Atom
Steric Number: The steric number is the number of atoms bonded to the central atom plus the number of lone pairs on the central atom. For bromine in HBrO₃:
- Number of bonded atoms: 3 (two oxygens and one OH group)
- Number of lone pairs: 0
- Steric Number: 3
Molecular Geometry: With a steric number of 3 and no lone pairs on the central atom, the molecular geometry is trigonal planar.
In summary, the most stable Lewis structure of HBrO₃ has bromine double-bonded to two oxygens and single-bonded to a hydroxyl group, all atoms have zero formal charges, and the molecule exhibits a trigonal planar geometry with specific bond dipoles based on electronegativity differences.
For a visual representation and further clarification, you can refer to this video tutorial on drawing the Lewis structure for HBrO₃:
videoHow to Draw the Lewis Dot Structure for HBrO₃: Bromic acidturn0search0