Chapter 8, Problem 99A

Interpretation Introduction

Interpretation:

Boron trihydride $\left({\text{BH}}_{\text{3}}\right)$ forms coordinate covalent bonds with other molecules.

Concept introduction:

According to octet rule, to achieve a full set of valence electrons that is eight electrons in outermost shell atoms share, lose, or gain electrons. Noble gases show stable electron arrangement. This stable arrangement contains complete outer energy level and smaller potential energy compared to other electron arrangement.

Answer to Problem 99A

As B produces suboctets that means it contains stable configuration with less than eight electrons. Boron contains six electrons so; it can share a pair of electrons donated by other atoms. Hence, ${\text{BH}}_{\text{3}}$ forms coordinate covalent bonds results when pair of electrons of one atom donates to share with other molecules.

Explanation of Solution

In ${\text{BH}}_{\text{3}}$, B is a nonmetal of group 3, it produces three covalent bonds with other nonmetallic atoms.

B atom shares only six electrons to form an octet. Hence, B share a pair of electrons given by other atoms. A coordinate covalent bond result when both of the electrons of one atom donates to share with an atom or ion which requires two electrons to produce lower potential energy and stable arrangement of electrons.

Conclusion

By sharing of electrons a covalent bond is produced.