Final answer:
Nitrogen has a higher ionization energy than phosphorous because its electrons are in a lower energy level, closer to the nucleus, and are held more tightly, not because of a greater number of neutrons or electrons.
Step-by-step explanation:
When considering the statement "When compared to phosphorous, nitrogen has a higher ionization energy due to decreased number of energy levels", this refers to the fact that ionization energy tends to increase across a period due to an increasing number of protons which cause a greater attraction to electrons. In this case, nitrogen has a higher ionization energy than phosphorus. This is not because of a greater number of neutrons (which would be irrelevant since neutrons do not affect ionization energy) or electrons, but because nitrogen’s electrons are in a lower energy level compared to phosphorus, and thus are held more tightly by the nucleus.
The reason behind this trend is related to the concept of electron shielding and penetration. In nitrogen, electrons occupy the 2p subshell which is closer to the nucleus; in phosphorus, the additional electrons enter the 3p subshell, which is higher in energy and further away from the nucleus. Therefore, it requires less energy to remove an electron from phosphorus than from nitrogen.