AsF₅ molecule is trigonal bipyramidal. The hybrid orbitals used by As-atoms for bonding are

type of hybridisation = no.of lone pairs on central atom+ no.of sigma bonds = 5 + 0 = 5

Two bonds axial bonds  and three bonds are equitorial bonds.  Electron density is along the bonding axis(Z-axis).  

The d  -orbital having electron density along axis is ${\mathrm{d}}_{{\mathrm{z}}^2}$