Question

Iodine pentafluoride has which of the following hybridization? (a) \(\mathrm{d}^{2} \mathrm{sp}^{3}\) (b) \(\mathrm{dsp}^{3}\) (c) \(\mathrm{sp}^{3} \mathrm{~d}\) (d) \(\mathrm{sp}^{3} \mathrm{~d}^{2}\)

Short answer

The hybridization of iodine pentafluoride is \(\mathrm{sp}^3\mathrm{d}^2\).

Step-by-step solution

Determine the molecular formula of iodine pentafluoride

Iodine pentafluoride is represented by the chemical formula \( \mathrm{IF}_5 \). This means it consists of one iodine atom bonded to five fluorine atoms.

Count the total number of valence electrons

Iodine (I) is in group 17 of the periodic table and has 7 valence electrons. Each fluorine (F), also in group 17, has 7 valence electrons. Therefore, for \( \mathrm{IF}_5 \) there are \(1\times 7 + 5\times 7 = 42\) valence electrons in total.

Determine the steric number of the central atom

The steric number is the sum of the number of atoms bonded to the central atom and the number of lone pairs on the central atom. Iodine is bonded to 5 fluorine atoms. We also need to account for lone pairs, so let's consider the structure: iodine typically expands its octet. Here, there is 1 lone pair on the iodine atom due to the remaining electrons after bonding. Thus, the steric number is \(5 + 1 = 6\).

Determine the hybridization based on the steric number

A steric number of 6 indicates that the hybridization of iodine in iodine pentafluoride is \(\mathrm{sp}^3\mathrm{d}^2\). This corresponds to the arrangement of the orbitals that can accommodate the steric number.

Key concepts

Chemical Bonding

Chemical bonding describes how atoms come together to form molecules. In iodine pentafluoride ( IF_5 ), a molecule that exemplifies chemical bonding, iodine and fluorine atoms join through covalent bonds. Covalent bonds occur when atoms share electrons, providing stability to atoms by fulfilling the octet rule.
The octet rule is a principle that atoms seek to obtain eight electrons in their valence shell, resembling the electron configuration of noble gases. However, elements like iodine can expand their octet beyond eight electrons due to available d-orbitals, allowing the formation of hypervalent molecules like IF_5 .
In this molecule, iodine uses one of its d orbitals in addition to its p and s orbitals to form 5 covalent bonds with fluorine, leading to an area with high electron density and reinforcing the molecule's stability.

Valence Electrons

To understand a molecule's properties and its reactivity, grasping the concept of valence electrons is crucial. Valence electrons are the outermost electrons that participate in chemical bonding. For iodine and fluorine, both belong to group 17 of the periodic table, having 7 valence electrons each.
In the molecule IF_5 , iodine brings in 7 valence electrons, while each of the 5 fluorine atoms also contributes 7 electrons. Consequently, the total count of valence electrons in the molecule is 42. These electrons determine not only bonding but also the shape and reactivity of the molecule.
Understanding the distribution of these electrons allows chemists to predict how atoms will bond and the resulting molecular structure.

Steric Number

The steric number is a fundamental concept used to determine the molecular geometry and hybridization of a molecule. It is calculated by adding the number of atoms bonded to a central atom and the number of lone pairs present on the central atom.
In iodine pentafluoride, iodine is the central atom surrounded by five fluorines. It also has one lone pair of electrons. Therefore, the steric number for iodine here is 6 (5 from fluorines + 1 lone pair).
A steric number helps in identifying the electron domain geometry, which in turn reveals the hybridization. For IF_5 , a steric number of 6 tells us that iodine's hybridization is sp^3d^2 , essential in defining the molecule's three-dimensional structure.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. It provides crucial information about the molecule's shape and spatial layout.
For iodine pentafluoride ( IF_5 ), given its steric number of 6, its molecular geometry is described as "square pyramidal." This is due to the five bonded fluorine atoms and one lone pair around the central iodine atom.
The geometry influences both the physical and chemical behavior of the molecule. IF_5 's distinct arrangement arises because the lone pair occupies one of the equatorial positions, minimizing electron pair repulsion as per VSEPR theory. This theory aids in predicting the shape of molecules based on electron pairs looking for an optimal arrangement to reduce repulsive forces.