Nitrogen has a higher first ionization energy than phosphorus
CHEMISTRY · Single correct · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
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 2p subshell raises the energy of those electrons, so extra energy is needed to remove one.
(c) Nitrogen’s valence electrons occupy the 2p subshell, which is closer to the nucleus and experiences less shielding than the 3p 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 3p subshell, a more stable arrangement, so less energy is needed to ionize it than nitrogen.