c. Addition of the electrophile to the aromatic ring
Explanation:
The first step of the mechanism for electrophilic aromatic substitution is an addition, in which the electrophilic compound reacts with an electron pair of the aromatic system. This step generally needs to be catalyzed with a Lewis acid. This addition leads to the formation of a cyclohexadienyl carbocation. This carbocation is unstable, due to the presence of the load on the molecule and the loss of aromaticity. This is partly offset by the relocation of the positive resonance charge.
In order to solve for this you would need to plug it into an equation. You would add them all up to eachother after multiplying them by their percentages.
So it would be (0.75*48.90)+(0.18*49.10)+(0.07*50.20). Plug it all into a calculator and you get 49.027amu. Then you would round to significant figures so 49.03amu should be your answer.
All the elements in one group have the same number of valence electrons. ... Since elements in a group have the same number of valence electrons, they behave similarly in chemistry. An example would be the alkali metals (excepting hydrogen. Hydrogen is in this group only because it has one valence electron.