The first ionization potential refers to the energy needed to remove the most loosely bound electron from a neutral gaseous atom, converting it into a positive ion. Essentially, it reflects the strength with which an atom holds onto its electrons.

The ionization energy generally increases across a period on the periodic table due to an increase in the effective nuclear charge. However, there are specific trends and exceptions based on electron configuration and electron-electron repulsions in orbitals.

In analyzing the options provided:

• Boron (Z=5, Electron configuration: $$1s^2 2s^2 2p^1$$) - It has one electron in the 2p orbital.
• Carbon (Z=6, Electron configuration: $$1s^2 2s^2 2p^2$$) - Electrons start pairing up in the 2p orbital.
• Nitrogen (Z=7, Electron configuration: $$1s^2 2s^2 2p^3$$) - It has a half-filled p subshell (2p orbital), which is a particularly stable arrangement due to the equal distribution of electrons that minimizes repulsion.
• Oxygen (Z=8, Electron configuration: $$1s^2 2s^2 2p^4$$) - Here, one of the p orbitals begins to pair up, which introduces additional electron-electron repulsion.

Among these options, Nitrogen has the highest first ionization potential. This higher value is due to the added stability provided by the half-filled p subshell configuration in nitrogen, which strongly resists the removal of an electron. Moreover, its electron arrangement is symmetrically spread out, reducing electron-electron repulsions and providing extra stability, thus increasing the ionization energy.

Therefore, the correct answer is: Option C: Nitrogen