Periodic Trends Challenge Questions Chemistry 1. Why is the ionization energy required to remove the second electron from Na atoms so very much greater than that needed to remove the first electron? 2. Why does atomic radius decrease as you move right across a period? 3. Why is it easier to remove the first electron from Al atoms than it is to remove the first electron from Mg atoms? 4. What type of ion does the addition of an extra electron to a Group VII atom produce? 5. Why is there a general increase in electron affinity among the atoms of groups V, VI and VII?