Back bonding in boron trihalides () significantly affects their properties. Which of the following s — p Block Elements Chemistry Question

💡 Solution & Explanation

Back bonding is most effective when orbitals are of similar size ($2p-2p$ in $BF_3$). In $BI_3$, the large $5p$ orbital of I overlaps poorly with the $2p$ orbital of B, making back bonding weakest. Weaker back bonding leaves Boron more electron-deficient, increasing Lewis acidity.