Which is the correct sequence in the following properties? For the correct order mark (T) and for th — p Block Elements Chemistry Question
Question
Which is the correct sequence in the following properties? For the correct order mark (T) and for the incorrect order mark (F):<br>(a) Lewis acidity order : SiF4 < SiCl4 < SiBr4 < SiI4<br>(b) Melting point : NH3 > SbH3 > AsH3 > PH3<br>(c) Boiling point : NH3 > SbH3 > AsH3 > PH3<br>(d) Dipole moment order : NH3 > SbH3 > AsH3 > PH3
💡 Solution & Explanation
Step 1: The S-O bond length depends on the extent of dπ-pπ back-bonding from oxygen to sulfur. Electronegative substituents pull electron density away from sulfur, increasing its partial positive charge and enhancing back-bonding (which shortens the S-O bond). Step 2: Fluorine, chlorine, and bromine are highly electronegative and strengthen the double-bond character of the S-O bond through induction, making the S-O bond shorter in SOF2, SOCl2, and SOBr2. Step 3: In dimethyl sulfoxide, SO(CH3)2, the methyl groups are electron-donating (+I effect), which decreases the partial positive charge on sulfur, reduces back-bonding, and maximizes the S-O single-bond character and length. Thus, option (d) is correct.