Is IF5 polar or nonpolar- Polarity of IF5

Iodine pentafluoride is a colorless fuming liquid represented by the chemical formula IF₅. However, the impure form appears yellow. It is a powerful fluorinating agent mainly used as a solvent in chemical laboratories. The IUPAC name of IF₅  is iodine(V) fluoride.

Now coming to the main point, i.e., what is the chemical nature of the IF₅ molecule? Is it polar or non-polar? Well, it is a polar molecule. Let’s find out how.

Is IF₅ polar or nonpolar?

Iodine pentafluoride (IF₅) is a polar molecule. The central iodine (I) atom in IF₅ is surrounded by five fluorine (F) atoms forming a square pyramidal shape.

The electronegativity of the fluorine (F) atom is greater than the iodine (I) atom. Thus each I-F bond in the  IF₅ molecule is individually polar and thus possesses a specific dipole moment value.

The asymmetric shape of IF₅ further increases the polarity effect as the I-F dipole moments do not get canceled in the molecule overall. Thus, IF₅ is a polar molecule with a net dipole moment value of µ = 4.81 D.

What are polar and nonpolar molecules?

A covalent bond is polar if it is composed of two unlike atoms having an electronegativity difference ranging from 0.5 to 1.6 units. All the polar bonds have a specific dipole moment value.

Suppose the dipole moments of individually polar bonds are not canceled due to the asymmetrical shape and geometry of the molecule. In that case, the molecule will be polar, such as IF₅.

Hence a polar molecule has an unequal charge distribution present in it. Contrarily, if the charged electron cloud is evenly spread over the molecule, in that case, it will be a non-polar molecule overall.

The following three main factors influence the polarity of any covalently bonded molecule:

• Electronegativity.
• Dipole moment.
• Molecular geometry or shape.

In the next section, we will discuss how these factors apply specifically to iodine pentafluoride (IF₅) in confirming that it is a polar molecule. So, let’s begin.

Factors affecting the polarity of IF₅

Electronegativity

It is defined as the ability of an atom to attract a shared pair of electrons from a covalent chemical bond.  

Electronegativity decreases down the group in the Periodic Table of elements while it increases across a period.

Greater the electronegativity difference between bonded atoms in a molecule, the higher the bond polarity.

Both iodine (I) and fluorine (F) belong to group VII-A (or 17) of the Periodic Table. The electronic configuration of iodine is [Kr] 4d¹⁰5s²5p⁵, so it has 7 valence electrons available for bonding.

On the other hand, the electronic configuration of fluorine is 1s²2s²2p⁵. Thus each F-atom also has 7 valence electrons and needs one more electron in its valence shell to complete its octet. The 5 F-atoms thus form a single covalent bond with the central I-atom on each side of the IF₅ molecule.

Five valence electrons consumed in bonding out of the seven initially available leaves behind two valence electrons, i.e., one lone pair on the central I-atom in IF₅.

Fluorine is the most electronegative element in the Periodic Table (E.N = 3.98). Each F-atom is more electronegative than an iodine atom (E.N = 2.66). There is an electronegativity difference of 1.32 units between these two atoms.

As a result, the F-atoms strongly attract the shared electron cloud from each I-F bond in the IF₅ molecule. The bonded electrons are held significantly close to the fluorine atoms in each I-F bond.

Each F-atom thus gains a partial negative (F^δ-) charge, while the central I-atom being electron deficient, obtains a partial positive (I^δ+) charge. Thus, oppositely charged poles develop in the IF₅ molecule. That is why each I-F bond is polar in IF₅.

Dipole Moment

The dipole moment is the product of electrical charge (Q) and bond length (r) between two bonded atoms. It is a vector quantity expressed in Debye (D) units.

It is represented by a Greek symbol µ and measures the polarity of a bond.

It is noted that a molecule’s dipole moment depends on the electronegativity difference between the bonded atoms. The greater the electronegativity difference, the higher the bond polarity, resulting in a high dipole moment value.

It points from the partial positive (δ⁺) center to the partial negative (δ^–) center of a bond or molecule.

The dipole moment of individually polar I-F bonds points from I^δ+ to F^δ- due to the electronegativity difference between the I and F atoms.

As each I-F bond in the IF₅ molecule is polar, all I-F bonds also have a specific dipole moment value.

Molecular geometry

As discussed earlier, IF₅ consists of five I-F single covalent bonds, and 1 lone pair of electrons is present on the central I-atom. Thus, there are a total of 42 valence electrons in the IF₅ molecule overall.

According to the VSEPR theory of chemical bonding, IF₅ is an AX₅N₁-type molecule. Around the central iodine atom (A), there are five bond pairs (X) and only one lone pair of electrons (N).

The presence of a lone pair of electrons on the central I-atom leads to strong lone pair-bond pair electronic repulsions in the IF₅ molecule. These strong repulsions contribute to the distortion in the regular symmetry of the molecule.

The iodine pentafluoride (IF₅) molecule thus adopts an “asymmetrical square pyramidal” shape in which the bond angle is also reduced to 81.9° from an ideal F-I-F bond angle of 90°.

As a result, the individual I-F dipole moments do not get canceled in the asymmetric shape of the iodine pentafluoride (IF₅) molecule. There is an unequal distribution of the electronic charge over the molecule.

Thus, IF₅ is an overall polar molecule with a net dipole moment value of 4.81 D.

Difference between polar and nonpolar?

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FAQ

Summary

• Iodine pentafluoride (IF₅) is a polar molecule.
• It consists of five polar I-F bonds due to an electronegativity difference of 1.32 units between the bonded I and F atoms.
• Fluorine attracts the shared electron cloud strongly from each I-F bond.
• The asymmetric square pyramidal shape of the IF₅ molecule leads to an unequal electron cloud distribution in the molecule.
• Due to the unsymmetrical arrangement of atoms, the individual I-F dipole moments are not canceled in the molecule overall. Thus, IF₅ is polar (μ= 4.81 D).