Hard Practice — Advanced Set

Hard Practice — Chained p-Block Reasoning

Combine trends and structure: bond strength $\to$ acidity/stability of $HX$; size/repulsion $\to$ anomalous $F_2$; back-bonding $\to$ Lewis acidity of $BX_3$; inert pair $\to$ oxidation-state stability.

• $HX$ acidity: HF $<$ HCl $<$ HBr $<$ HI; oxidising power $F_2>Cl_2>Br_2>I_2$; bond enthalpy $Cl_2>Br_2>F_2>I_2$.
• Group-15 hydride basicity $NH_3>PH_3>AsH_3$; oxyacid acidity rises with oxidation state.