The f-block elements (lanthanoids and actinoids) are characterized by the filling of the inner f-orbitals. The electrons enter the (n-2)f orbitals. The general outer electronic configuration for these elements is $(n-2)f^{1-14}(n-1)d^{0-1}ns^2$. For lanthanoids specifically, n = 6, corresponding to the configuration $4f^{1-14}5d^{0-1}6s^2$ .