When iodine is dissolved in aqueous potassium iodide, 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 1: Identify the species involved
When iodine (I2) is dissolved in aqueous potassium iodide (KI), the species present are potassium ions (K+), iodide ions (I-), and the iodine molecule (I2).

### Step 2: Understand the reaction
The iodide ion (I-) can react with the iodine molecule (I2) to form the triiodide ion (I3-). This occurs because the iodide ion donates a pair of electrons to the iodine molecule.

### Step 3: Determine the structure of the triiodide ion (I3-)
The triiodide ion consists of three iodine atoms. One iodine atom acts as the central atom, while the other two iodine atoms are bonded to it. The central iodine atom has three lone pairs of electrons.

### Step 4: Calculate the steric number
The steric number is calculated as the sum of the number of bond pairs and lone pairs around the central atom. In the case of I3-:
- There are 2 bond pairs (the two iodine atoms bonded to the central iodine).
- There are 3 lone pairs.

Thus, the steric number = 2 (bond pairs) + 3 (lone pairs) = 5.

### Step 5: Determine the geometry
With a steric number of 5, the geometry around the central iodine atom is trigonal bipyramidal. In this geometry, the three lone pairs occupy the equatorial positions to minimize repulsion, while the two iodine atoms occupy the axial positions.

### Step 6: Determine the shape
When considering the shape of the molecule, we only account for the bonded atoms and ignore the lone pairs. The two iodine atoms bonded to the central iodine atom create a linear arrangement.

### Conclusion
Therefore, the shape of the species formed (triiodide ion, I3-) when iodine is dissolved in aqueous potassium iodide is **linear**.