Whether an element has an empty d orbital or not can be well understood from its atomic number. D orbitals can fit in maximum 10 electrons. So after filling the s and p orbitals, if there are still electrons remaining as per the electronic configuration, then these electrons go to the d orbital. So initially only one electron fills each of the 5 types of orbitals, and then if there are more electrons to fill, then they pair with the singly filled electrons in the same orbitals. Thus from the electronic configuration it is easy to say if an element has an empty d orbital or not.