Which compound—BH3 or BO3—would have polar covalent bonds? How do you know?
The compound BO3 would have polar covalent bonds.
To determine whether a bond is polar or not, you need to consider the electronegativity difference between the atoms involved in the bond. Electronegativity is the ability of an atom to attract electrons towards itself in a chemical bond.
In the case of BH3, boron has an electronegativity of 2.04, while hydrogen has an electronegativity of 2.20. Since the electronegativity difference is very small (0.16), the B-H bonds in BH3 are considered to be nonpolar covalent.
On the other hand, in BO3 (which is actually B(OH)3 or boron trihydroxide), boron still has an electronegativity of 2.04, while oxygen has an electronegativity of 3.44. The electronegativity difference is significant (1.40), indicating that the B-O bonds in BO3 would be polar covalent.
Therefore, the compound BO3 would have polar covalent bonds.