# Question #d7c8a

Nov 12, 2016

An adduct is the result of formation of a coordinate bond.

#### Explanation:

When two neutral species come together to form a coordinate bond, one of them provides both of the electrons in the bond.

In the case above, the nitrogen atom in $N {H}_{3}$ has a lone pair of non-bonding electrons that can be donated to form a coordinate bond to the boron atom in $B {F}_{3}$.

$B {F}_{3}$, on the other hand, has only 6 electrons in its valence shell (two electrons from each of the 3 BF bonds). It can accept a pair of electrons in its valence shell to form a complete octet (8 electrons) in its valence shell.

Because both electrons in the new B-F bond originated with $N {H}_{3}$, the bond is called a coordinate bond. The resulting product, ${H}_{3} N - B {F}_{3}$ is called an adduct.