Question

C1F3 can exist but FC13 cannot- Explain why?​

Answer 1

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.