Give the reason to explain why ClF3 exists but FCl3 does not exist.
Chlorine has empty d-orbitals and it acquires excited state at the time of bonding when electron from 3p-orbital are promoted to 3d-orbital and thus can exhibit a covalency of three. Fluorine cannot expand its octet due to the absence of empty d-orbitals in 2nd energy shell. Thus it cannot exhibit covalency more than 1. Hence ClF3 exists but FCl3 does not.
