The triiodide ion, I3-, exists, whereas the corresponding ion with fluorine, F3-, does not. The I3- ion has a linear structure in which two outer I atoms are each bonded to a central I atom. Although I3- is a known ion, F3- is not.
c. Which of the following statements about the existence of I3- versus the nonexistence of F3- is or are true?
i. The Lewis structure of I3- shows 12 electrons around the central I atom.
ii. Elements from the second row of the periodic table generally do not form hypervalent molecules and ions.
iii. An I atom can form a hypervalent molecule or ion more readily than an F atom because of the larger size of the I atom.

Key Concepts

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They help visualize the arrangement of electrons and the connectivity of atoms, which is crucial for understanding molecular geometry and reactivity. In the case of I3-, the Lewis structure indicates that the central iodine atom is surrounded by 12 electrons, illustrating its hypervalent nature.

Hypervalency

Hypervalency refers to the ability of certain atoms to expand their valence shell and accommodate more than eight electrons. This phenomenon is commonly observed in elements from the third period and beyond, such as iodine, which can form stable compounds with more than four bonds. In contrast, elements like fluorine, which are in the second period, typically do not exhibit hypervalency due to their smaller atomic size and the inability to accommodate additional electrons.

Periodic Trends in Bonding

Periodic trends in bonding refer to the patterns observed in the chemical behavior of elements as you move across or down the periodic table. For instance, larger atoms like iodine can form more complex bonding arrangements compared to smaller atoms like fluorine. This is due to factors such as atomic size, electronegativity, and the ability to stabilize additional electron pairs, which explains why I3- exists while F3- does not.