The iodine triiodide ion, or I3–, exhibits interesting bonding properties that can be understood through its ground state, promoted state, and hybridized state diagrams.
Ground State
In the ground state, iodine has five valence electrons, and when combined with two other iodine atoms, the electrons are arranged in their lowest energy configuration. The electron configuration focuses on minimizing energy and maximizing stability. Typically, each iodine atom contributes its valence electrons, resulting in a basic Lewis structure with a central iodine atom bonded to two peripheral iodine atoms.
Promoted State
In the promoted state, one of the lone pair electrons from the central iodine atom gets promoted to a higher energy orbital. This promotion is essential for understanding the formation of bonding pairs and provides insight into the molecular geometry of the ion. The promoted state allows for the formation of three equivalent bonds, which is necessary for the tri-atomic nature of I3–.
Hybridized State
The hybridized state results from the combination of atomic orbitals to form new hybrid orbitals, which then allow the central iodine atom to form bonds with the peripheral iodine atoms. In I3–, the central iodine undergoes sp3 hybridization. This hybridization corresponds to the equivalent bond angles and molecular geometry, indicating a trigonal bipyramidal shape. The resulting structure is depicted with three identical single bonds between the central and terminal iodine atoms.
In summary, the ground state, promoted state, and hybridized state of the I3– ion illustrate the processes of electron configuration, molecular bonding, and the resulting symmetry, ultimately informing our understanding of its chemical properties.