Using only the periodic table arrange the following elements in order of increasing ionization energy: \[ \text { germanium, bromine, selenium, gallium } \] Lowest Highest

To arrange the elements germanium (Ge), bromine (Br), selenium (Se), and gallium (Ga) in order of increasing ionization energy, we can refer to their positions on the periodic table and the general trends in ionization energy. 1. **Ionization energy** generally increases across a period (from left to right) and decreases down a group (from top to bottom). 2. **Gallium (Ga)** is in group 13 and period 4. 3. **Germanium (Ge)** is in group 14 and period 4. 4. **Selenium (Se)** is in group 16 and period 4. 5. **Bromine (Br)** is in group 17 and period 4. Based on these positions: - **Gallium (Ga)** has the lowest ionization energy because it is the furthest left in the group. - **Germanium (Ge)** comes next, as it is to the right of gallium. - **Selenium (Se)** has a higher ionization energy than germanium, as it is further to the right. - **Bromine (Br)** has the highest ionization energy among these elements, being the furthest to the right. Thus, the order of increasing ionization energy is: **Gallium (Ga) < Germanium (Ge) < Selenium (Se) < Bromine (Br)**.