Explain why `CIF_3` exists where as `FCI_3` does not.

Explanation

`ClF_(3)` exists but `FCl_(3)` does not because
(i) Cl has vacant d-orbitals and hence, can show an oxidation state of +3 but F has no d-orbitals, therefore, it cannot show positive oxidation states. Further, since F can show only - 1 oxidation state therefore, it forms only ClF not `ClF_(3)`.
(ii) Due to larger size, Cl can accommodate three small F atoms around it, while F being smaller cannot accommodate three bigger sized Cl atoms around it.