To determine which of the elements has the largest first ionization energy, we can look at the trends in ionization energy within the periodic table. Generally, ionization energy increases across a period (from left to right) and decreases down a group (from top to bottom).
In this case, we have:
- Fluorine (F) in the second period
- Chlorine (Cl) in the third period
- Bromine (Br) in the fourth period
- Iodine (I) in the fifth period
Since fluorine is in the second period, it is higher up than chlorine, bromine, and iodine, which are all in lower periods.
In fact, the first ionization energies for these elements (generally) decrease as you move from fluorine to iodine due to increased atomic size and shielding effect.
Therefore, among these elements, fluorine (F) has the largest first ionization energy.
The correct answer is: A. fluorine