What would the Lewis dot structure look like for BrI2-

What would the Lewis dot structure look like for BrI2-? What is its electron geometry? What is its molecular geometry? Is it polar or nonpolar?

The correct answer and explanation is:

Lewis Dot Structure for BrI₂⁻:

To draw the Lewis structure for BrI₂⁻, follow these steps:

1. Count valence electrons:
   • Br (group 17): 7 valence electrons
   • Each I (group 17): 7 valence electrons × 2 = 14
   • Plus 1 extra electron for the negative charge: +1
     Total = 7 + 14 + 1 = 22 valence electrons
2. Determine the central atom:
   Bromine (Br) is less electronegative than iodine (I), so Br is the central atom.
3. Form single bonds between Br and each I:
   Use 2 electrons per bond → 2 bonds = 4 electrons used.
   Remaining = 22 – 4 = 18 electrons
4. Distribute remaining electrons to satisfy octets for outer atoms (I):
   Each I needs 6 more electrons (to complete 8).
   6 × 2 = 12 electrons used.
   Remaining = 18 – 12 = 6 electrons
5. Place remaining electrons on Br (central atom):
   Br gets the last 6 electrons as lone pairs.
6. Check for expanded octet:
   Br has 2 bond pairs and 3 lone pairs = 10 electrons.
   This is acceptable because Br can expand its octet (period 4 element).

Lewis Structure:

     I
     |
I — Br⁻ — I
     :
   .. ..

(Three lone pairs on Br, three lone pairs on each I.)

Electron Geometry:

• With 5 regions of electron density (2 bonding pairs + 3 lone pairs), the **electron geometry is trigonal bipyramidal.

Molecular Geometry:

• The 3 lone pairs occupy equatorial positions.
• The two I atoms occupy axial positions.
• Molecular geometry: Linear

Polarity:

• Although the molecule has polar bonds, the molecular geometry is linear and symmetrical, so dipoles cancel.
• BrI₂⁻ is nonpolar.

Summary:

• Lewis Structure: Br central with two I atoms and 3 lone pairs
• Electron Geometry: Trigonal bipyramidal
• Molecular Geometry: Linear
• Polarity: Nonpolar