Answer :
To determine which of the given statements are NOT true, let's evaluate each option:
A) Ionization energy generally increases as atomic radius decreases.
True. Ionization energy is the energy required to remove an electron from an atom. As the atomic radius decreases, the electrons are closer to the nucleus and held more tightly, making it harder to remove them, thus increasing the ionization energy.
B) Oxygen has a greater effective nuclear charge than nitrogen.
True. Effective nuclear charge is the net positive charge experienced by valence electrons. As we move across a period in the periodic table, the nuclear charge increases while the shielding effect remains constant, meaning oxygen has a greater effective nuclear charge than nitrogen.
C) Oxygen has a greater ionization energy than nitrogen.
False. Although oxygen has a higher effective nuclear charge, its ionization energy is actually slightly lower than nitrogen's. This is due to electron-electron repulsion in oxygen, which has paired electrons in its 2p orbitals, while nitrogen has half-filled p orbitals with one electron each, which is a more stable configuration.
D) Oxygen is more electronegative than nitrogen.
True. Electronegativity is the tendency of an atom to attract electrons towards itself. Oxygen is more electronegative than nitrogen because it has a higher effective nuclear charge.
E) Oxygen has less electron-electron repulsion than nitrogen.
False. In oxygen, there is more electron-electron repulsion because of the paired electrons in its 2p orbitals. In contrast, nitrogen's electrons in the 2p orbitals are unpaired and evenly distributed, causing less repulsion.
Based on the analysis, the statements C and E are NOT true. Therefore, the correct choices are C) and E).
