Bromine trifluoride is a yellowish interhalogen compound represented by the chemical formula BrF3. At room temperature, it is a fuming liquid with a pungent odor. BrF3 is a strong oxidizing agent and reacts violently with water, combustible materials, and acids. However, prolonged inhalation of BrF3 fumes is toxic to body cells.
Considering the many important applications of this chemical compound, we need to know its physiochemical properties. One such property is the chemical nature of BrF3, i.e., its polarity.
So, if you are curious to know whether bromine trifluoride (BrF3) is polar or nonpolar, then dive into this article and find out for yourself.
Is BrF3 polar or nonpolar?
Bromine trifluoride (BrF3)is a highly polar molecule. The central bromine (Br) atom in BrF3 is surrounded by three fluorine (F) atoms forming a T-shaped molecule.
A high electronegativity difference exists between the bonded Br and F atoms in each Br-F bond present in the BrF3 molecule. The asymmetrical T-shape of BrF3 further enhances the polarity effect.
The Br-F dipole moments do not get canceled, which leads to an overall non-uniform electron cloud distribution in the molecule. Hence BrF3 is polar (net µ =1.19 D).
The molecule is said to be polar if there is an unequal distribution of charge present in it. If the charge distribution is uniform in different parts of the molecule, then it is a non-polar molecule.
Three main factors control the polarity of any molecule, namely:
The electronegativity difference between two or more bonded atoms.
Dipole moment.
Molecular geometry or shape.
How do these factors contribute to an unequal charge distribution, and how do these apply specifically to BrF3 in confirming that it is a highly polar molecule?
Let’s uncover that insightful information in the detailed discussion below.
Factors affecting the polarity of BrF3
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 and increases across a period.
Greater the electronegativity difference between bonded atoms in a molecule, the higher the bond polarity.
Both fluorine and bromine belong to group VII-A of the Periodic Table. The electronic configuration of fluorine is 1s22s22p5, so it has a total of 7 valence electrons. Each F-atom is thus short of a single valence electron in order to achieve a complete octet electronic configuration.
On the other hand, the electronic configuration of bromine is 1s22s22p63s23p63d104s24p5, which also hints at the presence of 7 valence electrons available for bonding. The 3 F-atoms thus form a single covalent bond with the central Br-atom on each side of the BrF3 molecule.
Three valence electrons consumed in bonding out of the seven initially available leaves behind 4 valence electrons, i.e., 2 lone pairs on the central Br-atom in BrF3.
Atom
Electronic configuration
Valence electrons
Bromine (35Br)
1s22s22p63s23p63d104s24p5
7
Fluorine (9F)
1s2 2s2 2p5
7
According to the Pauling scale, an electronegativity difference of at least greater than 0.5 units between the bonded atoms makes a bond polar.
Fluorine is highly electronegative (E.N = 3.98) compared to bromine (E.N = 2.96). There is an electronegativity difference of 1.02 units between these two atoms.
So, F atoms strongly attract the shared electron cloud from each Br-F bond in the BrF3 molecule.The bonded electrons are held significantly close to the fluorine atoms in each Br-F bond.
Each terminal F-atom thus gains a partial negative (Fδ-) charge, while the central Br-atom gains a partial positive (Brδ+) charge. In this way, oppositely charged poles develop in the BrF3 molecule. As a result, each Br-F bond is strongly polar in BrF3.
Dipole moment
Dipole moment, represented by a Greek symbol µ, is a vector quantity measuring the separation between opposite electrical charges.
It is calculated as the product of the magnitude of charge (Q) and charge separation (r) between two atoms. It is expressed in Debye (D) units.
The direction of a dipole moment is from the center of the positively charged pole to the negative center and is dependent directly on the electronegativity difference.
Due to a great electronegativity difference between two bonded atoms, the bond polarity will be higher, leading to a high dipole moment value.
Considering the electronegativity difference between Br and F atoms, the dipole moment of individual Br-F bond points from Brδ+ to Fδ-.
Molecular geometry
As we have seen already, BrF3 consists of three Br-F covalent bonds, and 2 lone pairs are present on the central Br-atom (as shown below).
According to the Valence Electron Pair Repulsion (VSEPR) theory of chemical bonding, BrF3 is an AX3E2-type molecule. Around the central bromine atom (A), there are three bond pairs (X) and two lone pairs of electrons (E).
The ideal electron geometry of BrF3 is trigonal bipyramidal, considering a total of 5 electron density regions around the central atom. However, the presence of two lone pairs on the central Br-atom leads to strong lone-pair lone-pair and lone-pair bond-pair electronic repulsions. This repulsive effect distorts the symmetry of the molecule.
The molecule thus adopts an ‘asymmetric T-shape’’ in which the bond angle is also reduced to 86.2 ° from an ideal F-Br-F bond angle of 90 °.
The individual Br-F dipole moments do not get canceled in the asymmetric T-shape of bromine trifluoride (BrF3). The electron cloud stays non-uniformly distributed over the molecule as a whole. Thus BrF3 is polar (net µ = 1.19 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), bromine pentafluoride (BrF5), etc.
Examples include oxygen (O2), nitrogen (N2), methane (CH4), sulfur trioxide (SO3), etc.
One electron from the 4p atomic orbital on Br gets excited and goes to the empty 4d atomic orbital during chemical bonding.
One 4s, three 4p, and one 4d atomic orbitals of bromine thus hybridize to form five sp3d hybrid orbitals. The hybrid orbitals are not equivalent.
Two sp3d hybrid orbitals containing a pair of electrons behave as non-bonding electrons on the central bromine atom.
In comparison, the other three hybrid orbitals containing a single electron each form Br-F sigma bonds by sp3d-p overlap with the atomic orbitals of F-atoms.
How can we compare the polarity of BrF3 with that of BrF5?
Both bromine trifluoride (BrF3) and bromine pentafluoride (BrF5) are polar molecules. BrF3 possesses a T-shape, while the shape of BrF5 is trigonal bipyramidal.
But as both T-shape, as well as a trigonal bipyramidal shape, is asymmetric, therefore the dipole moments of individual Br-F bonds do not get canceled in either case. Thus both BrF3 and BrF5 are polar (net µ > 0).
Summary
Bromine trifluoride (BrF3) is a polar molecule.
It consists of polar Br-F bonds due to an electronegativity difference of 1.02 units between the bonded atoms.
Fluorine attracts the shared electron cloud from each Br-F bond.
The asymmetric T-shape of the molecule leads to a non-uniform charge distribution overall.
Dipole moments do not get canceled in the molecule. Thus, BrF3 is a polar molecule with a net dipole moment value of 1.19 D.
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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