The element with the electronic configuration $\left[Xe\right]4f^{7}5d^{1}6s^2$

After filling one electron in the 5d-orbitals, the filling of 4f-orbital begins, therefore , the elements  with the electronic configuration $\left(Xe\right)4f^{7}5d^{1}4s^2$  must be a f-block element