Effective nuclear charge and shielding Transitional Reasoning Download PDF

Questions

1. 1.

   A student analyzes the electrostatic forces experienced by valence electrons across the third period of the periodic table, specifically comparing neutral sodium ($Z = 11$) and neutral chlorine ($Z = 17$). Both atoms possess the same neon-like core electron configuration ($1s^2 2s^2 2p^6$), yet chlorine exhibits a significantly smaller atomic radius and a much higher first ionization energy than sodium. Based on the principles of nuclear shielding and effective nuclear charge ($Z_{\text{eff}}$), which statement correctly accounts for this periodic trend?

   • A) Chlorine's valence electrons experience greater shielding because additional valence electrons screen each other as effectively as core electrons.
   • B) Sodium's valence electron experiences a greater effective nuclear charge because fewer total electrons minimize mutual core electron repulsion.
   • C) Chlorine and sodium valence electrons experience identical effective nuclear charges because both elements share the same valence shell principal quantum number ($n = 3$).
   • D) Chlorine exhibits a much higher effective nuclear charge because its nuclear charge increases while the number of inner core shielding electrons remains constant.