Hard Practice — Advanced Set

Hard Practice — Chained Periodic Reasoning

Combine two or more ideas: effective nuclear charge + shielding to rank size; half-/fully-filled stability to explain ionisation-enthalpy anomalies; isoelectronic nuclear charge to order ionic radii; and position $\to$ property deductions.

• IE$_1$ (period 2): Li $<$ B $<$ Be $<$ C $<$ O $<$ N $<$ F $<$ Ne (anomalies at Be$>$B, N$>$O).
• Isoelectronic radius falls as nuclear charge rises; EGH: Cl $>$ F $>$ Br $>$ I.