Question

what is the molecular geometry of icl₃? (hint: start with a lewis structure) t-shape trigonal bipyramidal see-saw square planar square pyramidal

Explanation:

Step1: Determine the Lewis structure of \( \text{ICl}_3 \)

Iodine (I) is the central atom. Iodine has 7 valence electrons, and each chlorine (Cl) has 7 valence electrons. So total valence electrons: \( 7 + 3\times7 = 7 + 21 = 28 \).
In the Lewis structure, I is bonded to 3 Cl atoms. Each single bond uses 2 electrons, so 3 bonds use \( 3\times2 = 6 \) electrons. Remaining electrons: \( 28 - 6 = 22 \). These are placed as lone pairs. Iodine can have an expanded octet. After bonding, I has 3 bonding pairs and 2 lone pairs (since \( \frac{22 - 3\times6}{2} \)? Wait, no: total lone pairs on I: \( \frac{28 - 6}{2} - 3\times3? \) Wait, correct way: central I: 3 bonds (6 electrons) and lone pairs. The number of electron domains (bonding + lone pairs) on I: 3 bonding + 2 lone pairs = 5 (trigonal bipyramidal electron geometry).

Step2: Determine molecular geometry

For molecular geometry, we consider the arrangement of atoms (ignoring lone pairs). In a trigonal bipyramidal electron geometry with 3 bonding pairs and 2 lone pairs, the lone pairs occupy the equatorial positions (to minimize repulsion). So the three Cl atoms are in the axial and one equatorial? Wait, no: trigonal bipyramidal has 5 positions: 2 axial (top and bottom) and 3 equatorial (in a triangle). If there are 2 lone pairs, they go to equatorial positions (since lone pair - lone pair repulsion is more than lone pair - bond pair, which is more than bond pair - bond pair). So placing 2 lone pairs in equatorial positions, the three Cl atoms are in 1 equatorial and 2 axial? Wait, no: 3 bonding pairs and 2 lone pairs. So the molecular geometry (arrangement of atoms) is T - shape. Because the two lone pairs are in equatorial, and the three Cl atoms: one equatorial and two axial, but the angle between the axial and the remaining equatorial gives a T - shape. Let's recall: for \( \text{AX}_3\text{E}_2 \) (A = central atom, X = bonded, E = lone pair), the molecular geometry is T - shaped. \( \text{ICl}_3 \) has \( \text{AX}_3\text{E}_2 \) (I is A, 3 Cl are X, 2 lone pairs on I are E). So molecular geometry is T - shape.

Answer:

A. T - shape