Consider four elements from group 7a: fluorine in the second period, chlorine in the third period, bromine in the fourth period, and iodine in the fifth period. which element has the largest first ionization energy?

Out of the possible answers for this question, fluorine in the second period is correct. Of the four elements fluorine, chlorine, bromine and iodine, fluorine has the largest first ionization energy, with a Enthalpy number of 1681.0. Of all the elements, helium has the highest first ionization energy figure.