OF2 is the chemical formula for oxygen difluoride. Chemically, it is a very toxic and colorless gas having a molar mass of 53.99 g/mol. It is considered very dangerous due to its oxidizing properties. OF2 is extremely corrosive to eyes and skin if inhaled in high concentration.
To find out whether the oxygen difluoride OF2 molecule is polar or non-polar, continue reading the article.
Is OF2 polar or non-polar?
Oxygen difluoride (OF2) is a polar molecule. OF2 consists of a total of three atoms. One oxygen (O) atom is present at the center of the molecule, while the two fluorine (F) atoms occupy terminal positions, one on each side.
Fluorine is the most electronegative element in the Periodic Table, with an electronegativity value of 3.98. In contrast, the electronegativity value of an oxygen atom is 3.44.
Therefore, a small electronegativity difference of 0.54 units exists between the bonded atoms in each O-F bond in the OF2 molecule. Thus both O-F bonds are weakly polar with a specific dipole moment value in OF2.
However, it is due to the asymmetrical bent shape of OF2 that the dipole moments of both O-F bonds do not get canceled in the molecule overall. As a result, the electron cloud distribution does not stay uniform thus, OF2 is overall polar (net µ = 0.3 D).
A molecule is polar if there is a non-uniform charge distribution present in it. If the charge distribution gets equally balanced in different parts, then that molecule or molecular ion is considered non-polar.
The following three factors mainly influence the polarity of a molecule or molecular ion:
The electronegativity difference between two or more covalently bonded atoms
Dipole moment
Molecular geometry or shape
Now, let us discuss the effect of the above three factors one by one to prove that the oxygen difluoride (OF2) is overall polar.
Factors affecting the polarity of oxygen difluoride (OF2)
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.
Oxygen (O) is present in Group VI A (or 16) of the Periodic Table. The electronic configuration of an oxygen atom is 1s2 2s2 2p4. Valence electrons in oxygen are a total of 6 in number, so an O-atom has a deficiency of 2 more electrons for it to complete its octet.
However, Fluorine (F) is a halogen present in Group VII A (or 17) of the Periodic Table. The electronic configuration of a fluorine atom is 1s2 2s2 2p5. There are a total of 7 valence electrons in the F-atom. Therefore, each F-atom lacks 1 electron in order to achieve a stable octet electronic configuration.
In OF2, the central O-atom is single covalently bonded to a terminal F-atom, one on each side of the molecule. 4 valence electrons of oxygen consumed in covalent bonding out of a total of 6 initially available results in one lone pair of electrons on it. Each terminal F-atom also contains 3 lone pairs in OF2.
The presence of a lone pair of electrons on the central O-atom of OF2 creates repulsions in the bonded pair of electrons. Thus, the molecule adopts an asymmetrical bent or V-shape.
Atom
Electronic configuration
Valence electrons
Oxygen (8O)
1s2 2s2 2p4
6
Fluorine (9F)
1s2 2s2 2p5
7
There is an electronegativity difference of 0.54 units between the bonded oxygen (E.N = 3.44) and fluorine (E.N = 3.98) atoms in each O-F bond in the OF2 molecule.
Thus, the oxygen atom present at the center of OF2 gains a partial positive charge (Oδ+), while each of the terminal fluorine atoms acquires partial negative (Fδ-) charges.
As a result, both O-F bonds are individually polar in the oxygen difluoride molecule.
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.
The dipole moment of a polar covalent bond conventionally points from the positive center to the center of the negative charge. So in OF2, the dipole moment of both O-F polar bonds points from central Oδ+ to terminal Fδ-atoms. (as shown below).
Molecular geometry
According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, OF2 is an AX2E2-type molecule. To one O-atom at the center (A), two F-atoms (X) are attached, and there are two lone pairs (E) on the central oxygen atom.
So, the molecular geometry or shape of OF2 is bent, also known as angular or V-shaped. Each F-O-F bond angle is 103° in OF2.
The presence of two lone pairs of electrons on the central oxygen atom in OF2 leads to strong lone pair-lone pair and lone pair-bond pair electronic repulsions along with a bond pair-bond pair repulsive effect.
This strong repulsive effect pushes the bonded atoms away from the lone pairs at the center and decreases the bond angle to 103°. Thus, OF2 adopts an asymmetrical bent shape, also known as angular or V-shape.
It is due to this bent shape that the dipole moments of both O-F bonds do not get canceled in OF2. The electron cloud stays non-uniformly distributed over the molecule. Thus, OF2 is overall polar (net µ = 0.3 D).
Difference between polar and nonpolar?
Polar molecule
Non-polar molecule
Atoms must have a difference in
electronegativity
Atoms may have the same or different electronegativity values
Unequal charge distribution overall
Equal charge distribution overall
Net dipole moment greater than zero
Net dipole moment equals to zero
Examples include water (H2O), ethanol (CH3CH2OH), ammonia (NH3), sulfur dioxide (SO2), bromine trifluoride (BrF3), oxygen difluoride (OF2), etc.
Examples include oxygen (O2), nitrogen (N2), methane (CH4), nitrate [NO3]– ion, etc.
An electronegativity difference of 0.54 units exists between the bonded oxygen and fluorine atoms in each O-F bond in the OF2
Thus, both O-F bonds possess a specific dipole moment.
It is due to the asymmetrical bent shape of OF2 that the dipole moments of the O-F bonds do not get canceled.
Hence, oxygen difluoride (OF2) is a polar molecule overall (net µ = 0.3 D).
Why, among NH3, NF3, H2O, and OF2 is the dipole moment of H2O at a maximum?
H2O is the most polar molecule out of all four mentioned. This is because a high electronegativity difference of 1.24 units exists between the bonded hydrogen and oxygen atoms in each O-H bond in the H2O molecule.
The bent shape of H2O further enhances the polarity effect; thus, H2O is polar (net µ = 1.85 D).
A comparatively smaller electronegativity difference of 0.84 and 0.94 units exists in each of the N-H and N-F bonds in the NH3 and NF3 The trigonal pyramidal shape of these molecules keeps the polarity effect intact. Net µ (NH3) = 1.46 D while net µ (NF3) = 0.24 D.
The net dipole moment of OF2 is 0.3 D. It is only slightly polar due to an extremely small electronegativity difference of 0.54 units in each O-F bond.
Why oxygen difluoride OF2 molecule is polar, but the dioxygen difluoride O2F2 molecule is non-polar?
The oxygen difluoride (OF2) molecule has an asymmetrical bent. The dipole moments of individually polar O-F bonds do not get canceled in the OF2 molecule. Thus, it is overall polar (net µ = 0.3 D).
The dioxygen difluoride O2F2 molecule contains two F-atoms and two O-atoms. Both the O-atoms are single-covalently bonded to each other and present as the central atoms. While both F-atoms occupy terminal positions.
Each of the central O-atom contains two lone pairs of electrons; therefore, F2O2 has two bents that form a symmetrical open book-like structure. The dipole moments of O-F bonds get equally canceled on each side of the molecule. Thus, it is overall non-polar (net µ = 0).
What are the formal charges present on bonded atoms in OF2?
Formal charge on an atom = [ valence electrons – non-bonding electrons- ½ (bonding electrons)]
For the central O-atom
Valence electrons = 6
Bonding electrons = 4
Non-bonding electrons = 2 lone pair = 4
∴ Formal charge on the central O-atom = 6 – 4 – 4/2 = 6 – 4 – 2 = 6 – 6 = 0
Zero formal charge is present at the central O-atom and also on both F-atoms in oxygen difluoride.
Thus, the net formal charge present on the OF2 molecule is (0) + (0) + (0) = 0.
Summary
Oxygen difluoride OF2 is a polar molecule.
It consists of two polar O-F bonds having an electronegativity difference of 0.54 units between the bonded oxygen and fluorine atoms.
Oxygen difluoride OF2 has an inverted V or bent shape with a 103° bond angle.
The electron cloud is not uniformly distributed in the OF2 bent shape.
It is due to two lone pairs of electrons present on the central O-atom in OF2 that it adopts an asymmetrical bent shape. Consequently, the dipole moments of individually polar O-F bonds do not get canceled.The net dipole moment in OF2 is 0.3 D, so it is overall polar.
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
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