The bond polarities in BH3 are , the molecular shape is , and the molecule is
The Correct Answer and Explanation is:
The bond polarities in BH₃ are polar, the molecular shape is trigonal planar, and the molecule is nonpolar.
Explanation:
BH₃, or borane, consists of one boron atom and three hydrogen atoms. To understand the polarity of the bonds and the molecule as a whole, we must examine both electronegativity and molecular geometry.
Firstly, the B–H bonds are polar. This is because there is a difference in electronegativity between boron and hydrogen. Boron has an electronegativity of approximately 2.0 while hydrogen’s is about 2.1. Though this difference is small, it still results in slightly polar covalent bonds with a dipole moment pointing from boron to hydrogen.
Secondly, the shape of the BH₃ molecule is trigonal planar. Boron has three valence electrons and forms three single bonds with three hydrogen atoms. There are no lone pairs on the boron atom, which allows the molecule to adopt a trigonal planar geometry with 120-degree bond angles. This symmetric arrangement is crucial in determining the overall polarity of the molecule.
Despite the polar nature of each B–H bond, BH₃ is a nonpolar molecule. This is due to its molecular symmetry. The three polar B–H bonds are arranged symmetrically around the boron atom, and the dipole moments cancel each other out. As a result, there is no net dipole moment in the molecule, making BH₃ nonpolar overall.
In summary, BH₃ has polar bonds due to the electronegativity difference between boron and hydrogen. However, its trigonal planar geometry causes the bond dipoles to cancel, rendering the molecule nonpolar. This example illustrates how both bond polarity and molecular shape must be considered to determine the overall polarity of a molecule.
