Consider the elements bromine and chlorine; which element has a higher ionization energy? chlorine or bromine

Chlorine has a higher ionization energy than bromine. Ionization energy is the energy required to remove an electron from the atomic orbitals. Since chlorine has 3 energy levels, but bromine has 4, this implies that the outermost electrons of chlorine are nearer to the electron, and are more strongly held by attractive forces. This is why it takes more ionization energy to remove an electron from chlorine.