Why is carbocation positive?

Jun 25, 2016

Because around the carbon centre there are only $5$ $\text{electrons}$.

Explanation:

For carbon, $Z = 6$, and thus there are $6$ positive nuclear charges.

For methane, $C {H}_{4}$, there are $2$ inner shell electrons i.e. ($1 s$), and 8 electrons in the $4 \times C - H$ bonds. Carbon has a half share of these, and thus the carbon atom is presumed to be associated with $6$ electrons that precisely balance the $Z = 6$ nuclear charge to give a formally neutral carbon.

For a carbocation, ${R}_{3} {C}^{+}$, there are only 5 electrons associated with the carbon; and hence the carbon bears a formal positive charge.

Let's try another question. Dichlorcarbene $C {l}_{2} C :$ is not something you could put in a bottle; it is a species with which you could do a reaction. Can you tell me the formal charge of $\text{dichlorcarbene}$?