Give reasons:
`CIF_(3)` is known but `FCl_(3)` is not known.

Explanation

Chlorine atom has a vacant d -orbital which can easily accommodate 3 small fluorine atoms to form `ClF_(3)` . However, due to the absence of such vacant d-orbital in fluorine, it cannot accommodate 3 large chlorine atoms. So, `ClF_(3)` is known but `FCl_(3)` is not known.