When iodine is dissolved in aqueous potassium iodine, the shape of the species formed is :

Options

A. linear
B. angular
C. triangular
D. see-saw

Answer

To determine the shape of the species formed when iodine is dissolved in aqueous potassium iodide, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Species Involved**:
- When iodine (I2) is dissolved in aqueous potassium iodide (KI), it dissociates into potassium ions (K⁺) and iodide ions (I⁻). The iodine molecule (I2) interacts with the iodide ions.

2. **Understand the Formation of Triiodide Ion**:
- The iodine molecule (I2) can react with iodide ions (I⁻) to form the triiodide ion (I3⁻). This occurs because one of the iodine atoms from I2 can bond with the iodide ion, resulting in I3⁻.

3. **Draw the Lewis Structure**:
- For the triiodide ion (I3⁻), we have three iodine atoms. The central iodine atom is bonded to two other iodine atoms, and it has three lone pairs of electrons.
- Each iodine atom contributes 7 valence electrons, and since we have 3 iodine atoms and an additional electron due to the negative charge, the total number of valence electrons is 7*3 + 1 = 22 electrons.

4. **Determine the Steric Number**:
- The steric number (SN) is calculated as the number of bonded atoms plus the number of lone pairs. In I3⁻, there are 2 bonded iodine atoms and 3 lone pairs on the central iodine atom.
- Therefore, SN = 2 (bonded) + 3 (lone pairs) = 5.

5. **Identify the Geometry**:
- According to VSEPR theory, when the steric number is 5, the electron pair geometry is trigonal bipyramidal. The arrangement of the lone pairs and bonded atoms will influence the shape.

6. **Determine the Molecular Shape**:
- In a trigonal bipyramidal geometry with three lone pairs, the lone pairs will occupy the equatorial positions to minimize repulsion. This leaves the two iodine atoms in the axial positions.
- The resulting shape, when considering only the bonded atoms and ignoring the lone pairs, is linear.

### Conclusion:
The shape of the triiodide ion (I3⁻) formed when iodine is dissolved in aqueous potassium iodide is **linear**.