Chemistry
Chemistry
Problem
Nitrogen has a higher first ionization energy than phosphorus. Which statement most accurately accounts for this observation? a) Nitrogen has a greater effective nuclear charge than phosphorus, so its valence electrons are held more tightly and require more energy to remove. b) Greater electron–electron repulsion in nitrogen’s compact subshell raises the energy of those electrons, so extra energy is needed to remove one. c) Nitrogen’s valence electrons occupy the subshell, which is closer to the nucleus and experiences less shielding than the electrons of phosphorus, resulting in a stronger Coulombic attraction that is harder to overcome. d) When phosphorus loses one electron it attains a half-filled subshell, a more stable arrangement, so less energy is needed to ionize it than nitrogen.Intuitive explanation
The key is understanding how electron configuration and orbital stability interact. Nitrogen's outermost electrons occupy a half-filled orbital set—a particularly stable arrangement—while phosphorus's electrons sit in a larger, more diffuse orbital farther from the nucleus. Even though phosphorus is larger overall, nitrogen's electrons are held more tightly by the extra stability of that half-filled subshell, making them harder to remove.
Intuitive explanation
The key is understanding how electron configuration and orbital stability interact. Nitrogen's outermost electrons occupy a half-filled orbital set—a particularly stable arrangement—while phosphorus's electrons sit in a larger, more diffuse orbital farther from the nucleus. Even though phosphorus is larger overall, nitrogen's electrons are held more tightly by the extra stability of that half-filled subshell, making them harder to remove.