Fluorine has an atomic number of 9. then n=1 energy level has two elections, and the n=2 energy level has seven electrons. fluorine’s valence is a) +2 b) -2 c) +1 d) -1

The dotted line shows a new potential energy diagram with a shorter activation energy hill than that in the original potential energy diagram.

Explanation:

Activation energy is the extra amount of energy required by the reactants to cross the energy barrier to get converted into products.

When a catalyst is added, it lowers down the activation energy which is shown by a dotted line. As now less energy is required,  more of reactants can cross the energy barrier and get converted to products and thus increase the rate of reaction.

A catalyst increases the rate of reaction for both exothermic and endothermic reactions.