Question

which element has greatest ionization energy? Potassium or bromine

Answer 1

The ionization energy ‒ amount of energy required to remove the most loosely bound electron, the valence electron, of an isolated gaseous atom to form a cation.
K + energy = K^+ + e^‒
Metals usually have 1‒3 valence electrons (1 valence electron in case potassium) and their ionization energy very low. Bromine have greater than potassium ionization energy
Answer: Bromine