Is IF5 polar or nonpolar- Polarity of IF5

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if5 polar or nonpolar

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 IFis 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.

Name of moleculeIodine pentafluoride (IF5)
Bond typePolar covalent
Molecular geometrySquare pyramidal
Polar or Non-polar?Polar molecule
Dipole moment4.81 D
Bond angle81.9º

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.

what you mean by polar and nonpolar molecule

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.

AtomElectronic configurationValence electrons
Iodine (53I)

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p5

7
Fluorine (9F)1s2 2s2 2p57

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

each I-F bonds in IF5 is polar charge distribution 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.

dipole moment representation

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

dipole moment in IF5

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.

what is lewis structure of IF5

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°.

why is IF5 polar molecule

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?

Polar moleculeNon-polar molecule
Atoms must have a difference in
electronegativity
Atoms may have the same or different electronegativity values
Unequal charge distribution overallEqual charge distribution overall
Net dipole moment greater than zeroNet dipole moment equals to zero
Examples include water (H2O), ethanol (CH3CH2OH), ammonia (NH3), sulfur dioxide (SO2), bromine trifluoride (BrF3), iodine pentafluoride (IF5), etc.Examples include oxygen (O2), nitrogen (N2), methane (CH4), sulfur trioxide (SO3), etc.

Also, check –

FAQ

Why is IF5 a polar molecule?

  • IF5 has polar bonds because of a definite electronegativity difference between bonded I and F atoms.
  • Due to its asymmetric square pyramidal shape, the dipole moments do not get canceled in the molecule overall.

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

What type of bonds is present in IF5?

IF5 possesses highly polarizable polar I-F single covalent bonds.

Why are the bond lengths in the IF5 molecule not equal?

The distortion present in the geometry of the IF5 molecule leads to unequal I-F bond lengths. The lone pair-bond pair repulsions push F atoms away from the center.

Thus, the fluorine atoms occupy two different positions in the molecule and consequently have two different bond lengths, i.e., 1.84 Å and 1.86 Å, respectively.

bond length in IF5

Why is IF5 polar while PF5 is a non-polar molecule?   

The asymmetric shape of the IF5 molecule leads to a non-uniform electron cloud, and the dipole moments do not get canceled. Thus, IF5 is a polar molecule.

Due to the symmetric trigonal bipyramidal geometry of PF5, the individual P-F dipole moments get canceled in opposite directions, Thus, PF5 is a non-polar molecule.

polarity of IF5 vs PF5

Is there a formal charge on the bonded atoms in the IF5 molecule?

Formal charge of an atom = [ valence electrons – non-bonding electrons- ½ (bonding electrons)]

For iodine atom

  • Valence electrons = 7
  • Bonding electrons = 10
  • Non-bonding electrons = 2

∴ The formal charge on the central iodine atom  = 7-2-10/2 = 7-2-5 = 7-7 = 0

For fluorine atoms

  • Valence electrons = 7
  • Bonding electrons = 2
  • Non-bonding electrons = 6

∴ The formal charge on each fluorine atom  = 7-6-2/2 = 7-6-1 = 7-7 = 0

Thus, no formal charge is present on the iodine pentafluoride molecule overall.

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).
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