Atomic radius Original Scenario-Based Download PDF

Questions

1. 1.

   A deep-space surveyor scans an uncharted moon and isolates neutral gaseous atoms of three Period 3 elements: sodium ($Z = 11$), phosphorus ($Z = 15$), and chlorine ($Z = 17$). To calibrate its electrostatic containment grid, the automated probe must sort these atoms from largest to smallest atomic radius. Which ranking correctly arranges these elements by decreasing atomic radius, along with the proper periodic trend rationale?

   • A) $\text{Cl} > \text{P} > \text{Na}$, because the addition of more electrons into the valence shell increases electron-electron repulsion and expands the electron cloud across the period.
   • B) $\text{P} > \text{Na} > \text{Cl}$, because the half-filled 3p subshell in phosphorus provides anomalous shielding that expands its valence boundary beyond that of alkali metals.
   • C) $\text{Na} > \text{P} > \text{Cl}$, because the number of occupied principal energy levels progressively decreases as nonmetallic character increases from left to right.
   • D) $\text{Na} > \text{P} > \text{Cl}$, because effective nuclear charge increases across the period while the number of occupied electron shells remains constant, drawing valence electrons closer to the nucleus.