- Draw the Lewis Dot Structure for ICI2.
- What are the electron pair and molecular geometries for ICI₂?
- Draw the bond moments and overall dipole moment for ICI2
The Correct Answer and Explanation is :
1. Lewis Dot Structure for ICl₂⁻
To draw the Lewis dot structure for ICl₂⁻, follow these steps:
- Step 1: Count the total number of valence electrons.
- Iodine (I): 7 valence electrons (Group 17)
- Chlorine (Cl): 7 valence electrons (Group 17)
- There are two chlorine atoms, so 2 × 7 = 14 valence electrons from chlorine.
- The negative charge adds one more electron, so the total number of valence electrons is:
(7 (\text{from I}) + 14 (\text{from Cl}) + 1 (\text{charge}) = 22) valence electrons. - Step 2: Connect the atoms.
- Place iodine (I) in the center as it is less electronegative than chlorine (Cl).
- Attach the two chlorine atoms to iodine with single bonds, each contributing 2 electrons.
- Step 3: Distribute the remaining electrons.
- After placing two single bonds (2 × 2 electrons = 4 electrons), we have 18 electrons left.
- Place lone pairs of electrons on each chlorine atom, giving each chlorine 6 more electrons (total of 8 electrons around chlorine).
- After placing 12 electrons on chlorine, we are left with 6 electrons.
- Place the remaining 6 electrons on iodine as three lone pairs.
The final structure will look like this:
Cl - I - Cl
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(3 lone pairs on I)2. Electron Pair and Molecular Geometries for ICl₂⁻
- Electron Pair Geometry: ICl₂⁻ has 22 valence electrons. The iodine atom is the central atom with 2 bonding pairs (from chlorine atoms) and 3 lone pairs of electrons. Therefore, the electron pair geometry is trigonal bipyramidal.
- Molecular Geometry: Since there are 3 lone pairs on iodine and 2 bonding pairs, the molecular geometry is linear. The lone pairs occupy the equatorial positions, which leaves the two chlorine atoms positioned 180° apart, making the molecular geometry linear.
3. Bond Moments and Dipole Moment for ICl₂⁻
- Bond Moments: In ICl₂⁻, each I-Cl bond is polar because chlorine is more electronegative than iodine, resulting in a partial negative charge on chlorine and a partial positive charge on iodine. Each I-Cl bond has a bond dipole moment pointing from iodine to chlorine.
- Overall Dipole Moment: The molecular geometry of ICl₂⁻ is linear, which means the bond dipoles in the molecule will cancel each other out. Since the two I-Cl bonds are symmetrically arranged opposite each other, their dipole moments cancel each other, leading to no overall dipole moment for ICl₂⁻.
Thus, despite the individual polar bonds, the linear arrangement of ICl₂⁻ means the molecule does not have a net dipole moment.