Final answer:
The first ionization energy of potassium is predicted to be a lot lower than 1500 kJ because potassium, being an alkali metal with only one valence electron, is more easily ionized than Argon, which is a noble gas with a full outer electron shell.
Step-by-step explanation:
When comparing the ionization energies of Argon (Ar) and Potassium (K), we must consider their positions on the periodic table. Argon, being a noble gas, has a higher ionization energy because its outer shell of electrons is full, making it more stable and less likely to lose an electron. In contrast, potassium is located to the immediate left of Argon, in the same period, but being an alkali metal, it has only one electron in its outermost shell. This electron is more easily removed due to weaker electrostatic interactions with the nucleus, as potassium has a larger atomic radius than Argon.
The predicted value for the first ionization energy of potassium is a lot lower than 1500 kJ because as you move from right to left across a period in the periodic table, the ionization energy decreases. This is due to a decrease in the electrostatic attraction between the valence electron and the nucleus, as well as the electron being at a higher energy level.