Why is the ionization energy of br lower than that of cl but higher than that of se?

The ionization energy of an element is influenced by its atomic structure and the ease with which electrons can be removed. Bromine (Br) has a higher ionization energy than chlorine (Cl) because it is located further away from the nucleus, resulting in less shielding and higher attraction for its outermost electron. Selenium (Se) has a lower ionization energy than bromine because it is in a higher energy level, making its outermost electron easier to remove.