Lanthanoids (La-Lu, Z=57-71) have general configuration [Xe]4f^(0-14) 5d^(0-1) 6$s^2$. Dominant oxidation state is +3 for all. They are silvery-white, soft metals that tarnish rapidly in air. All are paramagnetic except $La^{3+}$ (4$f^0$) and $Lu^{3+}$ (4$f^{14}$). Chemical properties are very similar (due to similar ionic radii from lanthanoid contraction), making separation extremely difficult — ion exchange chromatography is the modern method. Most form M2O3 oxides (basic), MCl3 chlorides, and M(OH)3 hydroxides. Basicity of hydroxides decreases from La(OH)3 to Lu(OH)3 as ionic radius decreases.