Question

Question #d7c8a

Answer 1

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 `NH_3` has a lone pair of non-bonding electrons that can be donated to form a coordinate bond to the boron atom in `BF_3`.

`BF_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 `NH_3`, the bond is called a coordinate bond. The resulting product, `H_3N-BF_3` is called an adduct.