He electron-domain geometry and molecular geometry of iodine trichloride are _ and _, respectively.
A) trigonal bipyramidal, trigonal planar
B) tetrahedral, trigonal pyramidal
C) trigonal bipyramidal, t-shaped
D) octahedral, trigonal planar e) t-shaped, trigonal planar
The Correct Answer and Explanation is:
The correct answer is c) trigonal bipyramidal, t-shaped.
Explanation
Iodine Trichloride (ICl₃) is a chemical compound formed from one iodine (I) atom and three chlorine (Cl) atoms. To understand its geometry, we need to analyze both the electron-domain geometry and the molecular geometry.
- Determining the Electron-Domain Geometry:
- Iodine has 7 valence electrons. When it forms ICl₃, it shares electrons with three chlorine atoms, resulting in the formation of three single bonds. This uses three of iodine’s valence electrons. Iodine also has two lone pairs of electrons that remain non-bonded.
- The total number of electron domains around the central iodine atom is 5: three bonding pairs (I-Cl bonds) and two lone pairs.
- According to the VSEPR (Valence Shell Electron Pair Repulsion) theory, when there are five electron domains, the electron-domain geometry is classified as trigonal bipyramidal. This geometry consists of three equatorial positions and two axial positions.
- Determining the Molecular Geometry:
- While the electron-domain geometry considers all electron pairs (both bonding and lone pairs), molecular geometry focuses only on the arrangement of the atoms.
- In ICl₃, the two lone pairs occupy equatorial positions in the trigonal bipyramidal geometry to minimize repulsion, which leaves the three chlorine atoms in a T-shaped arrangement in the equatorial plane.
- Thus, the molecular geometry of iodine trichloride is classified as T-shaped due to the presence of the two lone pairs.
In summary, iodine trichloride exhibits a trigonal bipyramidal electron-domain geometry due to five electron domains (three bonding pairs and two lone pairs), and its molecular geometry is T-shaped as it only considers the positions of the chlorine atoms.