The similarity between Lithium and Magnesium is particularly striking and arises because of their similar sizes: atomic radii, Li = 152 pm, Mg = 160 pm: ionic radii: Li+ = 76 pm, Mg2+ = 72 pm. The main points of
(i) Both lithium and magnesium are harder lighter than other elements in the respective groups.
(ii) Lithium and magnesium react slowly with water. Their oxides and hydroxides are much less soluble and their hydroxides decompose on heating.
(iii) The oxides, Li2O and MgO do not combine with excess oxygen to give any superoxide.
(iv) The carbonates of lithium and magnetism decompose easily on heating to form the oxides and CO2 .
(v) Both LiCl and MgCl2 are soluble in ethanol.
(vi) Both LiCl and MgCl2 are deliquescent and crystallize from aqueous solution as hydrates, LiCl.2H2O and MgCl2.8H2O.