Draw the Lewis dot structure for ICl4- including all the lone pair electrons. Use solid and dashed lines to show 3D geometry if needed. What is the molecular geometry of ICl4-?
The Correct Answer and Explanation is:
Lewis Dot Structure for ICl₄⁻ (Iodine Tetrachloride Anion):
- Total Valence Electrons:
- Iodine (I): 7 valence electrons
- Chlorine (Cl): 4 atoms × 7 electrons = 28
- One extra electron due to negative charge: +1
- Total: 7 + 28 + 1 = 36 valence electrons
- Central Atom:
- Iodine is the central atom because it is less electronegative and can expand its octet.
- Bonding:
- Each Cl forms a single bond with Iodine → 4 bonds × 2 electrons = 8 electrons used
- 36 – 8 = 28 electrons left
- Lone Pairs:
- Place 6 electrons (3 lone pairs) on each Cl atom → 4 × 6 = 24 electrons used
- 28 – 24 = 4 electrons remain
- These remaining 4 electrons are placed as 2 lone pairs on the central Iodine atom
Final Lewis Structure:
lessCopyEdit Cl
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Cl—I—Cl
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Cl
Each Cl has 3 lone pairs. Iodine has 2 lone pairs.
To represent 3D geometry:
lessCopyEdit Cl
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Cl — I — Cl
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Cl
With solid wedge and dashed wedge, show square planar shape:
lessCopyEdit Cl
|
Cl — I — Cl
/ \
Cl Cl
(Use one Cl with a solid wedge and one with a dashed wedge to indicate positions above and below the plane.)
Molecular Geometry:
The electron geometry of ICl₄⁻ is octahedral, due to six regions of electron density (4 bonds + 2 lone pairs).
However, the molecular geometry (based on atom positions) is square planar because the two lone pairs occupy opposite positions, canceling out their repulsion symmetrically.
This geometry minimizes repulsion between lone pairs and bonding pairs by placing lone pairs 180° apart in axial positions. As a result, the four Cl atoms lie in the same plane, forming a square around the central Iodine atom. The Cl–I–Cl bond angles are approximately 90°.
