Using The Following Structure Of PBr3: :Br: 1 :Br-P-Br: Is The Molecule Polar Or Non-Polar? O Polar Non-Polar
The correct answer and explanation is:
The molecule PBr₃ (phosphorus tribromide) is polar.
Explanation :
Phosphorus tribromide (PBr₃) has a trigonal pyramidal molecular geometry. This shape results from the presence of three bonded bromine atoms and one lone pair of electrons on the central phosphorus atom. The structure can be represented as:
:Br:
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:Br-P-Br:
Polarity and Electronegativity
Polarity depends on two main factors: the presence of polar bonds and the overall geometry of the molecule. A bond is considered polar when there is a difference in electronegativity between the bonded atoms. Bromine (Br) has an electronegativity of 2.96, while phosphorus (P) has an electronegativity of 2.19. This difference (about 0.77) makes the P–Br bonds polar, with bromine pulling electron density toward itself due to its higher electronegativity.
Molecular Shape and Dipole Moments
Although the bonds are polar, the geometry of the molecule determines whether the dipole moments (vectors representing bond polarity) cancel each other out. PBr₃ has a trigonal pyramidal shape, which is asymmetrical. The lone pair on phosphorus pushes the three P–Br bonds downward, creating a non-uniform distribution of electron density. This asymmetry means the individual bond dipoles do not cancel out, resulting in a net dipole moment.
Why PBr₃ Is Polar
- Polar Bonds: The P–Br bonds are polar due to the difference in electronegativity.
- Asymmetrical Shape: The trigonal pyramidal geometry prevents dipole moments from canceling out.
- Lone Pair Contribution: The lone pair on phosphorus amplifies the asymmetry of the molecule.
In conclusion, the combination of polar bonds and an asymmetrical shape makes PBr₃ a polar molecule with a net dipole moment. The polarity of PBr₃ is important in determining its physical and chemical properties, such as solubility and reactivity.