Looking at the elements from period three, you can identify element 2 based on element 3. It shows that element 3 is Magnesium. The ionization energy increases as it goes from left to right.
Since Element 2 has a lower ionization, just think of an atom that is to the left of Magnesium because it has a lower ionization energy. The only atom to the left of Magnesium is Sodium. So element 2 is Na, or Sodium.
