The similarity between lithium and magnesium is particularly striking and arises because of

their similar size: atomic radii, Li = 152 pm, Mg = 160 pm; ionic radii : Li + = 76 pm, Mg 2+ = 72 pm. The main points of similarity are :

🔾 Lithium and magnesium react slowly with water. Their oxides and hydroxides are much less soluble and their hydroxides decompose on heating. Both form a nitride, Li 3 N and Mg 3 N 2 , by direct combination with nitrogen .

🔾 The oxides, Li 2 O and MgO do not combine with excess oxygen to give any superoxide.

🔾 The carbonates of lithium and magnesium decompose easily on heating to form the oxides

and CO 2 . Solid hydrogencarbonates are not formed by lithium and magnesium.