Question

Lewis structures can be used to understand why some molecules react in certain ways. Write the Lewis structure for the reactants and products in the following reactions.

a. Nitrogen dioxide dimerizes to produce dinitrogen tetroxide.

b. Boron trifluoride accepts a pair of electrons from ammonia, forming_{${\mathbf{\text{BF}}}_{\mathbf{3}}{\mathbf{\text{NH}}}_{\mathbf{3}}$}.Give a possible explanation for why these two reactions occur.

Short answer

a. Nitrogen dioxide dimerizes to produce dinitrogen tetroxide. This is because of which odd- electron species are very reactive.Boron trifluoride accepts a pair of electrons from ammonia, forming ${\text{BF}}_3{\text{NH}}_3$.

b. This is because the boron atom satisfies the octet rule by accepting a lone pair of electrons from_{${\text{NH}}_3$}.

Step-by-step solution

Define the octet rule

The octet rule is a chemical rule of thumb that represents the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, resulting in an electronic configuration similar to that of a noble gas.

Lewis structures of the two compounds

(a)

Lewis structures of $N{O}_2$and $\left({\text{N}}_2{\text{O}}_4\right)$ are as follows:

According to the Lewis structures, $N{O}_2$ has an odd number of electrons, and therefore, cannot satisfy the octet rule.

This is because of which odd- electron species are very reactive.

Process of dimerization

The one unpaired electron on each $N{O}_2$molecule pair up, yielding a species whose Lewis structure can satisfy the octet rule.

Thus, the odd electron species are very reactive.

Boron trifluoride and the lewis structures

(b)

Boron trifluoride is the inorganic compound with the formula ${\text{BF}}_3$.It is a useful Lewis acid and a versatile building block for other boron compounds. On the other hand ammonia is a compound of nitrogen and hydrogen with the formula _{${\text{NH}}_3$}.

Lewis structures of ${\text{BF}}_3,N{H}_3$and ${\text{NH}}_3-{\text{BF}}_3$ are as follows:

All the boron trihalides form simple Lewis complexes with suitable bases, as in the reaction shown below:

${\text{BF}}_3+{\text{NH}}_3\to {\text{BF}}_3-{\text{NH}}_3$

is an electron deficient because boron has only six electrons around it.

The lone pair on the nitrogen atom of an ammonia molecule is used to overcome this deficiency, and a compound is formed involving a coordinate bond

Therefore, boron atom satisfies the octet rule by accepting a lone pair of electrons from ${\mathrm{NH}}_3$.