Draw the Lewis structure for ICl2–. How many lone pairs of electrons are around the central iodine atom? What is the formal charge for iodine atom? Describe the hybridization of the iodine atom and shape of the ion. (15 pts)
The Correct Answer and Explanation is :
The Lewis structure for the ICl₂⁻ ion can be drawn step by step:
- Count the total number of valence electrons:
- Iodine (I) is in Group 17 (7 valence electrons).
- Each chlorine (Cl) atom is also in Group 17 and has 7 valence electrons.
- The ion has a negative charge, which means there is one extra electron.
- Therefore, the total number of valence electrons is:
[
7 \, (\text{from I}) + 7 \times 2 \, (\text{from Cl}) + 1 \, (\text{extra electron due to charge}) = 15 \, \text{electrons}.
]
- Draw the skeletal structure:
- Iodine is the central atom, as it is less electronegative than chlorine.
- Each chlorine atom forms a single bond with iodine.
- Distribute the electrons:
- Two electrons are used to form the I-Cl bonds.
- After forming the bonds, 13 electrons remain.
- These remaining electrons are placed as lone pairs around the chlorine atoms.
- Since each chlorine requires 3 lone pairs to complete its octet, that uses up 12 of the remaining electrons.
- The final electron is placed as a lone pair on iodine.
- Determine the formal charges:
- Iodine formal charge:
[
\text{Formal charge of I} = \text{Valence electrons of I} – \text{(Lone pairs on I + Bonded electrons/2)}
]
Iodine has 7 valence electrons, 2 lone electrons, and is bonded to two chlorine atoms, each contributing one electron. Thus, the formal charge on iodine is:
[
\text{Formal charge of I} = 7 – (2 + 2) = 3.
] - Chlorine formal charge:
Each chlorine has 7 valence electrons, with 3 lone pairs and one shared electron in the bond. Thus, the formal charge on each chlorine is:
[
\text{Formal charge of Cl} = 7 – (3 + 1) = 3.
]
- Hybridization and Shape:
The iodine atom has 3 regions of electron density (2 bonding pairs with Cl atoms and 1 lone pair). These 3 regions of electron density suggest sp² hybridization. The shape is T-shaped, according to the VSEPR theory, as there are 3 electron regions (2 bonding pairs and 1 lone pair), and lone pairs repel more strongly, causing the bonding pairs to form a T-shape.
Final Answer:
- Lone pairs on iodine atom: 1 lone pair
- Formal charge on iodine atom: 3
- Hybridization of iodine: sp²
- Shape of the ion: T-shaped